That’s true, although syphilis in general has a really tough time evolving resistance to antibiotics. It’s not necessarily true that we’ll inevitably get bacteria with resistance to all antibiotics—bacteria have a significant trade off to evolving resistance, since it usually decreases their overall fitness compared to wild type. That’s why you’ll typically see bacteria revert to sensitivity in the wild, and most multi drug resistant bacteria are only acquired from environments with lots of antibiotics (hospitals).

There’s also some drugs that are really difficult for bacteria to evolve dual resistance to—in S. aureus for example, it’s nearly impossible for them to simultaneously resist methicillin and vancomycin.

More infections = more mutations is also not necessarily true, especially since syphilis is a bacteria and covid a virus. A lot of bacteria have more proofreading materials to prevent mutations, and bacteria that like to form biofilms will have lower rates of mutation. Bacteria also have longer competition against themselves and the microbes around them as they grow coupled with a lower reproduction rate, which enforces more selective pressure than on viruses.

Viruses don’t have a lot of these problems because they reproduce and mutate significantly faster, and they’re not susceptible to antibiotics. Antiviral treatments are a lot harder to target because viruses rely on the host more than bacteria, so a lot of the “targets” are things our body also needs. That’s one of the reasons a lot of antivirals have more common side effects and than antibiotics.