I think it was the perfect storm of sickness/tiredness/anger/and his speech issues that become magnified with any of the above. And he was never a spring chicken, but he has been doing the job just fine, but the media suddenly saw a way to cash in on their constant both sides bullshit and jumped on the "Biden old" train along with the fascists.
Is he old, yes. And he should have long since retired, but he is still alert enough to have a conversation with people and make decisions, both of which have been glaring issues for Trump.
If anything the media should worry about their constantly giving a platform to fascist talking points and fear of losing revenue because they are "taking sides". I think reporting on the real issues surrounding Trump and Project 2025 is perfectly valid without needing to "balance" their reporting with something negative about the democratic candidate. It's actually the job of the press to report the facts, not to always both sides everything to maintain a fake neutrality.