@raphjd
There are many jobs in the Federal Government where the "head" (even cabinet-level head) of the organization really doesn't need to know ANYTHING about the ACTUAL WORKINGS of the agency they're "heading" - the day-to-day WORK of the agency is done by "career" Government employees. These "political appointees" are there to provide direction (goals & points of emphasis) and policy.
For example, I'd bet you that Pete Buttigeg couldn't name 5 different bridge construction base materials. But that doesn't mean he can't be a good Transportation Secretary! At that level of leadership, the details of the "job" are NOT what you're hired for - it's the leadership and direction-setting. (Mayor Pete will be deciding to "Fix that Bridge... and that one, too" not "Let's use a polymer concrete wearing surface system instead of rubberized asphalt."
Dr. Rachel Levine, as the Assistant Secretary of Health can provide MUCH NEEDED and VALUABLE guidance on the health needs of the LGBTQ community without having to know the difference between Bikarvy and Dovato.
Is it good that she's a health professional? Absolutely! Is there possibly, anywhere, someone POSSIBLY more qualified? Sure, that's actually probable! But the mix of competence AND personal qualities makes her a ground-breaking and inspiring choice!
Now, with that said, it's also the case that, when you put someone at the top who really is CLUELESS about the department they head (and, to be sure, that is NOT the case with Dr. Levine), real damage can be done. Betsy DeVos. Enough said.