1)
Why were their clothes torn?
1.
Rashi (from Sanhedrin 60a): They heard blasphemy, which is like cursing Hashem [for which one must tear]. Radak (Melachim II, 18:36) - this is an Asmachta that one who hears blasphemy of Hashem must tear his clothes 1 . Equating Hashem to other gods (just like they did not save from me, so Hashem - verse 20) is the ultimate blasphemy! Also Hashem called it blasphemy - "Es Mi Cherafta v'Gidafta; Cherafta Hashem" (37:23-24).
1
Radak: This is only if he hears from a Yisrael. Chazal had a tradition that Ravshake was a Yisrael Mumar.
