From the US' POV, having Syria devolve into a theocracy is a small price to pay for the harm this inflicts on Russia (most notably losing their only port on the Mediterranean and forcing them to transit through the Hellespont, subject to the whims of Turkey)
Not really. Al-Assad was a known quantity and the relationship, while certainly not friendly, was at least stable (by Middle-Eastern standards). These guys on the other hand are an unknown, and that lack of predictability makes neighbours uneasy.
Israel literally already annexed some new territory out of Syria. Al-Assad supported the Palestinian resistance and Hezbollah through weapons transfer. This is an undeniable less for Palestine and Lebanon.