The definition of mistake has always included actions done on purpose. Consider the sentences: Getting on that Boeing jet was a huge mistake. The worst mistak

The definition of mistake has always included actions done on purpose. Consider the sentences: Getting on that Boeing jet was a huge mistake. The worst mistake I ever made was voting for Trump. Having an intern give him a blowjob was the biggest mistake of Clinton's career. In all of those cases the action was done on purpose. You are confusing the definition of mistake with the phrase "by mistake", i.e. "I ran rm -rf by mistake", which means unintentionally.