Was it a one-time sudden realization, a nagging feeling you couldn't get rid of, or a back-and-forth process?
For me, it was 5 or so years of back-and-forth waffling between vegan and "reducitarian/VAH" before a very strong dose of magic mushrooms a few years ago gave me a stern kick in the ass about my own ethics and hypocrisy, which is how I finally stayed vegan. The same trip was the beginning of my political radicalization left as well.
Friend was vegan. I made fun of her in hs but were still friends. Eventually realized she wasn't joking and I was like "oh."
Also I love to make my boss and coworkers feel uncomfortable like they need to accommodate me. Yes, nerd, accommodate.