The Tree is dying!
The centuries-old hope for Moshiach (symbolized by the Tree)*
It's on the verge of extinction before the Coming of Moshiach, thanks to the four signs:
1. Increase in informers (strong winds),
2. Decrease in students (decaying roots),
3. Depletion of funds (de-fertilized soil) and (hence)
4. Giving up on the Redemption).
What will be??!
From the stump of that tree, a new shoot blooms and begins to grow.
The Prophet goes on to describe the new shoot as the ultimate Moshiach, detailing his actions and wide-ranging impact on the world at the End of Days.
Big Forest Vs. Jewish Tree
This prophetic battle is ultimately referring to the End of Days:*
When that "forest" would reappear...
Like the powerful assimilating forces of
of modern times,
which are naturally overtaking and consuming,
propagating assimilation of everyone and everything.
Yet the Jewish Tree would be concurrently challenged
by the Four Signs, which attempt to quash the hope of the Jewish People for the Coming of Moshiach and promote assimilation.
How will the tree survive??!
It is then when a new shoot from the roots of that tree will rise.
Moshiach will then come.*
The prophecy continues to describe how Moshiach will restore those Four Signs:
וְשָׁפַ֚ט בְּצֶ֙דֶק֙ דַּלִּ֔ים
Veshafat betzedek dalim
And he shall judge the poor justly
Restoring Jewish support by getting the rich to invest their (charity) funds appropriately.*
וְהוֹכִ֥יחַ בְּמִישׁ֖וֹר לְעַנְוֵי־אָ֑רֶץ
Vehochiach bemishor leanvei aretz.
and he shall reproach with equity the humble of the land
Returning the number of students (those who were humbled / put down by the informers and/or forest), and with a soothing reproach*, will attract everyone to become his students.*
וְהִכָּה־אֶ֙רֶץ֙ בְּשֵׁ֣בֶט פִּ֔יו
Vehika eretz beshevet piv
and he shall smite the land with the rod of his mouth
The "land" here refers to the wicked people (the informers) of the same land where the humbled suffered.*
וְהָ֥יָה צֶ֖דֶק אֵז֣וֹר מָתְנָ֑יו וְהָֽאֱמוּנָ֖ה אֵז֥וֹר חֲלָצָֽיו
Vehaya tzedek ezor motnav vehaemuna ezor chalatzav.
And righteousness shall be the girdle of his loins,
and faith the girdle of his loins
Intimating faith (a hidden trait*) through his righteousness (a visual trait*) to his direct followers*, and through them to the rest of the world (as the verses continue to describe).
NOTES & REFERENCES
The tree represents the hope for Moshiach: since the first three of the four signs allude to circumstances (winds, roots and soil) whereas the forth sign of the tree being too old is analogous to the hope for Moshiach that's taken a long time to being fulfilled.
Parables in Torah (by the Maharal) are regarded as exact in all their details (as opposed to just helping understand things on the surface, because the parable stems from the referent -- Likutei Sichot Vol. 1 p.83). In this case, there's another analogy used by the Prophet Isaiah to describe Moshiach as the sprouting of a new tree. This will also help us understand why the original tree has to go.
The Forest and the new shoot: Isaiah Ch. 10 and start of Ch. 11. Here are the relevant verses:
"(10:5) Woe that Assyria is the rod of My wrath... (7) But he does not deem it so... (8) For he says... (11) "Indeed, as I did to Samaria and to her idols, so will I do to Jerusalem and to her idols... (14) And my hand found the wealth of the peoples like a nest, and as one gathers abandoned eggs, I gathered the entire world, and no one moved a wing, or opened his mouth, or chirped." ... (16) Therefore, the Master, the L-rd of Hosts shall send leanness into his fat ones, and in the place of honor, a burning shall burn like the burning of fire... (18) And the glory of his forest and his stately forest, both soul and flesh shall it destroy, and it shall be as a tree eaten to powder by the worms. (19) And the remaining trees of his forest shall be few, and a lad shall write them... (33) Behold the Master, the L-rd of Hosts lops off the branches with a saw, and those of lofty height are hewn down, and the tall one shall be humbled. (34) And the thickets of the forests shall be cut off with iron, and the Lebanon shall fall through a mighty one.
(11:1) And a shoot shall spring forth from the stem of Jesse, and a twig shall sprout from his roots... (4) And he shall judge the poor justly, and he shall chastise with equity the humble of the earth, and he shall smite the earth with the rod of his mouth and with the breath of his lips he shall put the wicked to death. (5) And righteousness shall be the girdle of his loins, and faith the girdle of his loins. (6) And a wolf shall live with a lamb... (9) for the land shall be full of knowledge of the Lord as water covers the sea bed.
Also note Moshiach called and compared to a plant in a few prophecies like Jeremiah 23:7, Zechariah 2:8, as well as our daily prayers (15th blessing).
Sanherib has exiled and mixed up all the nations: Mishna Yadayim 4. Note he is the only superpower in history (per se) to have done and be successful in transplanting and eliminating whole nations, hence the significant danger of this episode in comparison with other historic hostile superpowers. His power of assimilation also then ties in with the Forest simile, as the single tree will have to acclimatize to the surrounding forest.
G-d miraculously cleared the mighty Assyrian Army ("Forest"): An angel came that night before they planned to attack Jerusalem, and killed 185,000 of them (Kings II 19:35).
The tree (representing Davidic Dynasty) seems to have been included in the forest that's been cleared out: So it seems and hence there's a need for the staff to come out from the remaining stump and the shoot to sprout from the original roots. Because otherwise why do we need a new and soft shoot when we have the primary solid tree? The old tree has to go as will be explained further. This then ties in with the Maharal's analogy of the dying tree.
The Big Forest Vs. the Little Shoot ultimately alludes to the End-of-Days Encounter: Vast majority of commentators on Isaiah 11:1. Also note the connection between these two episodes: The divine will for Chizkiyah – the king of Judea at that time – to be Moshiach and Sanherib – the king of Assyria – to be "Gog and Magog" (being the ultimate battle before the ultimate Redemption): Talmud Sanhedrin 94a. And the contrast between the two episodes: The threat in Chizkiyah's time (Sanherib, the Forest) was external to the Jewish People and the religious situation of Judea was one of the best ever (Talmud, ibid), whereas at the End of Days the spiritual situation of the Jewish People is at a record low as the danger of the forest (assimilation) has penetrated well inside them (thanks to the Four Signs).
Moshiach will come when the Jewish Tree is about to die: That's what the Four Signs are literally about ("Moshiach won't come until..."), as well as Isaiah's prophecy of the new shoot (Moshiach) rising following the danger of the forest.
Moshiach will get the rich to properly invest their (charity) funds: Metzudat David on Isaiah 11:4.
Moshiach will have a soothing approach to reproach: Rashi et al on Isaiah 11:4.
The whole world will become students of Moshiach: Isaiah 2:2, Rambam. Laws of Repentance 9:2
Ridding of the wicked from the Land: See Radak on Isaiah 11:4 explaining why the word "wicked of (the land)" is seemingly missing as the verse has already mentioned "the humble of the land". This could hint to a more subtle way that Moshiach will deal with the remaining informers (Jews). Also note the end of verse 4 – וּבְר֥וּחַ שְׂפָתָ֖יו יָמִ֥ית רָשָֽׁע / uvruach sefatav yamit rasha / and with the breath of his lips he shall put the wicked to death – refers to the real wicked gentiles (see Targum) and even those will be dealt with subtly (Biur Hagrah).
Moshiach intimating faith (hidden trait) through his righteousness (revealed trait): MALBIM on Isaiah 11:5.
Moshiach intimating faith to his direct followers: Rashi on Isaiah 11:5.