Early in the invasion of Ukraine Russia shared video of a functional hypersonic missle that could deliver nukes past all current air defenses. That was why he was hesitant to escalate by using long range missles.

If I remember right, since then we’ve found that Russias hypersonic missles cannot steer at hypersonic speeds and have had some misfires making them less of a threat. That plus the fact that Trump is months away from helping Russia, the strategy has changed.