That was one initial theory, but it's known to not be the cause. An earlier video that Steve Burke and Wendell from A1techs did had Wendell examine several hundred CPUs that were running in servers on non-Z790 motherboards (another source of potential problems that was initially blamed) at conservative settings, known and logged temperature for the lifetime of the server (so not temperature). He still saw about a 50% failure rate.

I also personally destroyed one of my CPUs with motherboard default settings, and the other with Intel's recommended settings (less aggressive than the motherboard defaults), so I can personally attest to this not just being people running with crazy voltages or something.

There may also be other issues that people have caused by doing something else, but the elephant in the room has been narrowed down to processors destroying themselves while running well within spec.