Could've sworn he was buddy buddy with the Clinton's and everyone knew it. Regardless, WikiLeaks leaked Hillary emails showed he supported Hillary.
WikiLeaks was one of the greatest organizations in the history of the world. Easy to see why US gov't is trying to destroy Assange/them.
Well, let's be frank...
He was in his position during Bill Clinton's administration. As a result, he would absolutely have come across Hillary, especially since she was promoting a health care plan.
After Clinton's terms, I'm sure if they had a good relationship from his time in office they'd probably have remained at least cordial afterwards--I don't know if that's "exchanging Christmas cards" or if it's "being buddy buddy", but it's not like he just disavows any personal relationship with an outgoing President just because a new one shows up.
Then, he was in Obama's administration while she was Secretary of State. It's not to say that an infectious disease expert would be in a close working relationship with SecState, but I'm sure they crossed paths.
So, he had a choice in 2016 between supporting someone with a history in politics / public roles, someone he had personal knowledge of and a personal relationship with (and I'm assuming a level of mutual respect/trust)... Or a brash reality TV star with absolutely no experience...
One doesn't have to assume he supported Hillary because Fauci is a raging leftist Democrat. The simpler explanation is that he was supporting the woman he knew, and who he thought capable, over someone that he didn't know and whose public persona left grave doubt about his temperament for the job.