"Reports from in vitro studies suggest that ivermectin acts by inhibiting the host importin alpha/beta-1 nuclear transport proteins, which are part of a key intracellular transport process that viruses hijack to enhance infection by suppressing the host’s antiviral response." -Some random google search, I dunno, source is the NIH.

So that implies the thought process is "virus stops something that produces immune response, Ivermectin stops virus from stopping that process while it does its own thing that is mostly unrelated, and the body begins a more immediate immune response, leading to quicker/safer recovery."

As most data says Ivermectin use doesn't matter much in people who were already sick, only those healthy did it make any difference, this theory makes loose sense, since by the time you're notably sick, the body is already producing immune responses, the virus already has a foothold, but obviously not a lot of study is done on it.