There were a few contributing factors.
1; Spirituality. It is true that Pagans in history have ate and sacrificed animals. However, they also had an affinity with them, and those I identify with treated them greatly with dignity and respect, often employing prayers and rituals in order to ease their passing. Furthermore, the animals were hunted in the wild. In today’s day and age, however, animals, even “free range” animals, are often existing in abysmally poor conditions unfit for any living creature. I find the way they are treated to be disgusting.
2; Eco-friendly. The mass production of meat, and thus the mass, cramped housing of animals, produces incredible amounts of toxic gases and other waste products which detrimentally effect the environment.
3; Sustainability. Did you know that one acre of land can produce 40,000ibs of tomatoes, 53,000ibs of potatoes, yet only 137ibs of beef? We are at a critical point in time in which overpopulation is becoming an ever increasing risk, and it is extremely inefficient to continue in this manner.
4; Ethics. While I identify with certain forms of Pagans, I myself, purely as an individual, do not agree with cruelty towards animals. I’m even reluctant to get rid of a moth for my girlfriend for fear of inadvertently killing it.
In short, I think that the mass production of meat is crippling. When mankind only killed what it needed, the world was a better place. When mankind treated animals with dignity and respect, the world was a better place. The truth is that being a Vegetarian is one small way through which I can regain a little faith in the world, by believing that while the world may commit countless sins a day, I can at least attempt to reduce mine. I’m embarking on a path to become a better person, and this was the first step.
Thank you for your question; I hope my answer was sufficient.