Why is he not taking this seriously?

He is. Support for Israel is policy, not politics. It's not Biden supporting Israel... it's the entire US political establishment that does.

You might just as well ask Biden to stop the US from being imperialist - no member of the US political establishment would ever do that. Period.

This is why you see liberals everywhere heeding the clarion call to pre-emptively start looking for people to blame when Biden hands over to the GOP (the "bad cop") come November.