1)
Why were their clothes torn?
1.
Radak (from Sanhedrin 60a): It is because they heard blasphemy. 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 35) is the ultimate blasphemy! Also Hashem called it blasphemy - "Es Mi Cherafta v'Gidafta; Cherafta Hashem" (19:22-23).
1
Radak: This is only if he hears from a Yisrael. Chazal had a tradition that Ravshake was a Yisrael Mumar.
