Pretty sure it was Biden being a pussy and making it clear he can't run a kindergarten classroom, let alone a military action. Putin and Xi did NOTHING under Trump because love him or hate him, he's bat-shit insane. When he tells you "If you try to grab Taiwan/Ukraine I'm gonna nuke Bejing/Moscow," he very likely means it. And even if he doesn't is it worth the chance? You can do what you like to Biden, all he's gonna do is use strong language.