This isn't the "what radicalized you" line of questioning. I always read those as the last straw. I'm more interested in your first steps.
I know everyone's journey is different.
Mine was realizing that despite being a complete asshole, I give a fuck about everyone.
A complicated mix of
my parents being lefties (more so my dad, my mum is/was a socdem at best)
my great grandparents being part of the communist resistance during WWII
going to school with people who were rather right wing, and them being shitheads to me when I started listening to punk