2 facts: Ukrainian aid would end if Republicans got ANY even remotely valid wind of "Biden/democrats are arming terrorists via Ukraine". Of course Zelenskyy and co are not that stupid and are literally fighting for their existence and won't jeopardize it on something stupid and clearly evil like the terrorist attack.
2nd, Russia has every reason to attach any shred of evidence from the attack to Ukraine. It would actually give their people a reason to fight, which doesn't exist at all right now and hence the term special military operation.