Iran
The Israel Effect
An undercut Syria is advantageous to Israel since it would further disrupt the Iranian-Syrian-Hezbollah axis, which includes Hamas and the Houthis, with their plans to exterminate Israel.
However, as much as Israel wants to see Assad weakened enough so that Syria cannot be a real threat to Israel for many decades, his complete overthrow would bring turmoil and uncertainty to the area. In the end, a total triumph by either side of the contenders would probably strengthen an anti-Israeli regime.