Who go to Egypt?
Rashi: Hoshe'a ben Elah "sent messengers to Soa Melech Mitzrayim" (Melachim II, 17:4).
Radak: They go to request help. Malbim - amidst this, some people descended to stay there.
It says at the beginning of the Sefer (1:1) that Yeshayah prophesized in the days of Uziyah, Yosam, Achaz [and Chizkiyah]. We do not find that they requested help from Egypt!
Malchei Yehudah did not request, but Hoshe'a ben Elah (Melech Yisrael) requested (Rashi).
Radak (1) #1: Do not say that it refers to Tzidkiyah, for later it discusses the salvation in the days of Chizkiyah! Rather, this was in the days of Achaz, even though it is not written in Sefer Melachim or Divrei ha'Yamim.
Radak #2: In the days of Chizkiyah, officers of Yehudah were not good. Chizkiyah needed great force to make them repent. Melech Ashur came against all fortified cities and seized them. Had they been good, this would not have happened to them! This Perush conforms with the coming Parshiyos. In every Parashah it says Kedosh Yisrael, for He was sanctified in Yisrael via the matter of Machaneh Ashur.
Why does it say "Laredes Mitzrayim"?
Rashi #1: Eretz Yisrael is higher than all other lands.
Rashi #2: This is a descent for them.
Radak: One who leaves Yerushalayim, he descends.
Why does it say "u'Fi Lo Sha'alu"?
Malbim: The Torah warned us not to return to Egypt.
Why does it say "La'oz b'Ma'oz Pharaoh"?
Malbim: This corresponds to "Linsoch Masechah" (1). This was foolish for two reasons. (a) They thought to be helped from Pharaoh; really, he will not save them, like it says below (31:1-3). (b) They accepted the authority of Egypt, to be frequently under its shade, and to be its slaves who bring a gift (tax).
What is "v'Lachsos"?
Rashi: It is to be sheltered.
