'...Biden, who sought escalation with Russia for decades...'

Yes, FOR DECADES. Not good, but it's the opposite of unpredictable. Having said that, it is true that Biden is a bit unpredictable. An example was his, as you put it, 'sabre-rattling' about Taiwan a few months ago. But what he said was not in line with declared U.S. policy. In his case, it may be due to the effects of old age.