Iranian regime has already weakened quite a bit, nobody even a couple years back expected Hamas and Hezbollah to be mute spectators in Iran-Israel war.
For Iran, Syrian influence is gone, Lebanon influence is becoming limited, IAF is using Iraq airspace right now.
There is internal dissent in Iran otherwise how do you explain the widespread penetration and space available to Mossad.
Re nuclear goal, US can target Iranian underground bunkers and infra more effectively. This would take their nuclear infra back to zero, with no AD US-Israel can consistently prevent resumption of the program.
Re regime change, there were no foots on ground in Syria for that regime change, there was an insurgency but internal revolt can still happen in Iran.