The article “Motives of consumers following a vegan diet and their attitudes towards animal agriculture” by Meike Janssen et al. describes the reasons why vegan people stopped eating meat and how they feel about livestock farming.

Their main findings are :
The persons following a vegan diet have three main motives for this diet : animal well-being-related motives (mentioned by 90% of the persons interviewed), motives related to personal well-being and/or health (69%), and environment-related motives (47%)
Most people (82%) have several reasons to stop eating meat, they don’t either just do it for self-oriented reasons (health for example) or just for ethical reasons (to save the animals or for the environment)
Around a third of the respondents were open to continue with livestock farming if there were vastly improved animal welfare standards put into place
Just to remind you and clear any doubt : veganism, food-wise, is when you refuse to eat any animal products. That means products where the animals have to be killed (meat, gelatin, etc) AND other animal products (eggs, dairy, etc).
But let’s go back to this study !

People also mentioned other interesting reasons for following this diet : 10% used motives labelled as ‘social justice’, related to world hunger, human rights, and the exploitation of humans for example. 5% of the respondents talked about their aversion to capitalism and/or the food industry.
What’s interesting too is that vegans are often seen as a homogeneous group of people with the same ideas : try to ban all types of farming and usage of animals. But here, the vegans interviewed are not always in agreement. For example, when they were asked if they agreed on the fact that nobody should keep any animal (pets or otherwise) 33% agreed while 32% disagreed. When they were told that farm animals could be comfortable there (with appropriate adaptations), 32% agreed while 51% disagreed.
The researchers tried to put the different respondents in different categories according to their motives (that’s what is called segmentation). What they found is that the group of vegan who are driven only by animal-related reasons had been generally following this diet longer than those driven also by self-related motives. One of the hypothesis could be that, with time, self-related reasons becomes less important whereas animal-related reasons becomes more important. Another hypothesis could be that there is a difference in motives between the former vegans and the new vegans.
So, as it’s often the case with groups of people, vegan people do not agree on everything and don’t have the same motives. Most importantly, their motives are not only animal-oriented, their personal heath and the environment are also essential in their choice to become vegans. Understanding that is imperative if you want to communicate towards those persons or invent new products for them.
Thank you for your attention ! Let me know what you thought !

Here is the link to the scientific paper : https://www.sciencedirect.com/science/article/abs/pii/S0195666316302677
Source : Janssen, M., Busch, C., Rödiger, M., & Hamm, U. (2016). Motives of consumers following a vegan diet and their attitudes towards animal agriculture. Appetite, 105, 643-651.