There's two sides to it. Russia of course wants the war to become a quagmire for everyone supporting Ukraine.
But the reason the US and Israel is even able to do what they are doing is because Russia is spending all its resources fighting Ukraine.
Russia is too weak to do anything to meddle in the conflict. Five years ago Russia would have its navy in the area, private militias on the ground and been an all around nuisance. Today they are non-existant outside of Ukraine.
A sound analysis on it:
Trump, Putin, and the war in Iran
I'm not sure if that's the reason why US and Israel pulled the trigger, twice.
But for sure it helped. It helped with Syria, Armenia, Venezuela, and now Iran.
But that doesn't explain why the current US administration continues to be submissive to what Russia is now: an isolated regional power - and even this is arguable because it will depend on the region.
Like, this is the biggest geopolitical blunder of modern Russia that will probably lead to the collapse of the federation (economic, demographic, diplomatic) - and this catering is all based on personal good relationship?
It just doesn't make any sense.