No doubt Biden's cognitive abilities are in decline, but I doubt that's the plan. This is the second time Team Crazy has tubed a bibartisan bill.
When a child keeps trying to touch a hot stove, a mother can keep saying "No, Billy, it's hot! You'll burn yourself." When the child keeps trying to touch it, at some point the mother needs to step back, have the burn cream and Band-Aid ready then let it play out.
IMO, that's what the Democrats, not just Biden, are doing on the political level. America voted, Trump and his oligarchs have made claims (often lies) and, after years of fighting MAGA morons, they've decided to step back and let it play out.