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.
I had already been vegetarian for over three years, and wasn't attached to milk or eggs, just thought it would be difficult to completely avoid them. Turns out it wasn't, and I've been vegan for years now. The /r/vcj memes helped give me the push too.
Coincidence (or not?): I was raised conservative (and omni, ofc), became a lib soon after i went vegetarian, and became a socialist at same time i went vegan.
haha dude. not a coincidence.
this is the way.