Grew up in a pretty standard rightwing house.

Got primed to leftism by losing at least 1 (you could argue 3 or 4 of them) family member to the American healthcare system/insurance. Had others suffer from poor care, high bills, the stupidest doctors, and/or not being able to pick the best options because of high bills. Family functionally shook itself apart over healthcare stress.

Eventually played frickin Victoria 2, which taught me some basic political literacy. IE: Liberals are more with what I identified with at the time, not "conservative". Also started realizing that socialists were the good guys. From there, it was a slow road to now, where I believe Stalin shouldn't have stopped at Berlin. Mostly a lot of little things, becoming more and more dissatisfied with liberals being unable/unwilling to enact any of their stated goals, agreeing more with socialist politics, being blamed for 2016 despite voting for Hilldog in a swing state (that she still lost), etc.