Not really a dumb reason, but back in the day I was stuck in the WordPress developer loop and tired of it. I was pretty familiar with a handful of languages, but wasn't doing much more than setting up themes and building out pages with builders.
One day I heard the CTO talking about a tool he would love to have but couldn't find anything that worked how he needed it to. The CTO was a big buzzword guy and recently shared an article with my manager at the time about how C++ was "the best language". So naturally I chimed in and told him I could build that tool easy peasy and I would use C++ obviously because it's the best language.
It was such a simple tool, basically just matching phrases and categories and spitting out a list of options. It took me months to make, but I learned a lot and it kind of worked for the most part and everyone was happy. I eventually got a de-facto department in the company where I would just build internal tools and handle some legacy codebases that they were previously outsourcing.
I later on got my current job because of that leap.
TLDR: I learned C++ because I was bored and lied that I already knew it.