It's not that he's blamed for CV19; he's blamed for his response to it. The fact that he abolished the Pandemic Response group as soon as he got into office didn't help matters, nor did his daily press conferences where he continually downplayed the scope of the Pandemic while thousands of people were dying.
As for the vaccines, I'll be happy to credit him with pushing the development that got us a vaccine in record time. The issue is a lot of his base are anti-vaxers, and so even as he was helping to get a vaccine developed, he was also saying you shouldn't take it, it's dangerous, and hey, why not just inject bleach? That'll kill the germs!