1)
Why did all the Chachamim gather?
1.
Malbim: We find (Perek 13) that Pelishtim were ruling over Yisrael. 1 Even though it said (7:13) that all the days of Shmuel, Hashem struck them, through perversion of judgment the enemy returned. 2 Yisrael saw no escape, so they gathered.
1
Radak (8): They did not come to request a king for war, for the only war was with Nachash Melech Amon (Perek 11. The verses imply that Nachash threatened Yisrael only after Shmuel anointed Sha'ul. - PF)
2
Malbim: We find that as long as Yehoshafat established Mishpat (Divrei ha'Yamim 2 20), "va'Ygaresh Mipanecha Oyev va'Yomer Hashmed" (Devarim 33:27).