What is the significance of this Nesher?
What is the meaning of "Kafnah Sharasheha"?
Rashi: It is an expression of hunger, like "l'Shod ul'Chafan" (Iyov 5:22). The roots of the vine were hungry and desired that Nesher. Malbim - they wanted to nurture from it and connect to it.
Tosefes in Rashi: It is like Asfah (gathered). [The letters] are reversed; it is like what Chachamim call Kenufiya (Shabbos 60b).
Radak: Tzidkiyah made his kingship dependent on Melech Egypt.
What is the meaning of "v'Daliyosav Shilchah Lo"?
Rashi: He sent his messenger [to water it].
Radak: Tzidkiyah sent a bribe to Melech Egypt, and served him.
Malbim: It sent its branches to [the Nesher] so it will water it me'Arugos Mata'ah. The first Nesher bent the branches to the ground and withheld from them water, so it will join with Shabbos 60b that go high; they will be lowered and connect to Tzaftzefah. [The vine] desired the 2nnsr, for there its branches will rise and drink much water. I.e. [Tzidkiyah] thought that via Pharaoh, his head will be lifted, and he will receive good influence and Brachah.
What are "me'Arugos Mata'ah"?
Rashi: From the Ugiyos (cavities dug around trees or vines) that the first Nesher made for it.
Malbim: [He requested Melech Egypt] to help him with his nation and great army [to protect him] from Melech Bavel. It is called me'Arugos Mata'ah, for Melech Bavel, who planted it, made patches to water it via them. I.e. he gave to Tzidkiyah authority to establish his kingship honorably, and Tzidkiyah asked Melech Egypt to help him, like Nebuchadnetzar, who made him king, helped and raised him.