As late as April 2020 he was telling people there was no need to mask or change their behaviors because Covid didn't seem to be a big issue in the US. He's on video saying this, if you can still find it (probably only available from right wing sources by now). When confronted about this, it never happened or it was taken out of context or he was right then but the science changed and now he knows better.

The problem with that argument is that science did know about how Covid spreads. Because we had years of data on SARS. Covid is SARS-2. But that would have involved working with other countries to share that science. The US hegemony can't let other countries tell it how to respond or what to think about the virus. Especially one of the largest countries impacted by it, China. The science didn't change, he just denied the science out of political expedience.

After that he should have stepped down because he's old anyways. But he's a careerist and narcissist. Obviously he's not the only qualified person to do the job, but he felt he was. The Democrats encouraged that idea.

The ad-hoc justification for denying the science became that he knew we had a PPE shortage and didn't want to make it worse. We had a shortage because Trump's son-in-law raided the program and sold all the inventory. Someone who wasn't even an elected official. Instead of saying that and being honest about it, he lied. Again, because he's a liberal and he had a duty to the office to not upset the administration. Yeah, Trump could have fired him but who cares. Then go on the lib media, which would have hailed him a martyr, and light his ass up. Pretty easy media strategy there.

Imagine denying science, throwing away public trust over Trump.

Also he was bad on the AIDS crisis as well. He was a proponent of the idea that constant close contact with people infected with HIV would spread it. That alienated a lot of victims from their friends and families and spread the panic.