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.
Flirted with buddhism. Luckily i actually read some buddhist texts and didn't look at online buddhists who are all like "well yes buddha says it is a stain in your karma to kill an animal BUT"
bruh
Anyway i realized vegans were right, went vegan overnight and haven't looked back since.