The opportunity

That makes good sense but since Russia is capable of hitting anyplace on Earth, any Nation standing in their way would be subject to attack if Russia went nuclear. The US and Russian MAD Treaty (Mutually Assured Destruction) would then be put into effect causing a nuclear response from the US. NATO would hesitate to invade Russia without US backing and support and Biden has already shown his weakness by allowing the Russian buildup that led to the invasion. The best way to turn Russia back would be for NATO to reject Ukraine as a member. This was the reason Putin used to invade. They didn't want NATO troops on their border. If that threat disappears, the reason to remain in Ukraine disappears too.