No we realized years ago. It’s the entire reason his campaign started the idea that he’d be a single term president. People brought it up after the midterms when he confirmed he’d run again. It’s been in the news and an open question ever since then. According to insiders, the debate was held early specifically to show he wasn’t too old.
Biden and the Party have been aggressively going after critics, accusing them of being Trump supporters and disloyal to the very concept of democracy. Which would have worked if he didn’t shit the bed so badly.