Is there any good analysis of the history of the vegan movement?

I was wondering recently how the vegan movement gained in numbers and visibility recently? A couple decades ago veganism was barely even known and now there's quite a few of us, vegan options starting to pop up everywhere. And hopefully this will keep going.

Why now? What has changed to make veganism rise in this century?

Is factory farming responsible for the rise in veganism by making it easier to find animal agriculture abject and then leading people to also refuse regular animal farming?

Did pets make us have more empathy towards animals?

Has there been some great activist(s) decades ago that made veganism start gaining traction?

Is this just the natural progression of social justice movements that started in the recent centuries?

When I see how hard it is to convert people to veganism now, I can't even imagine how hard it must have been to do so when the movement was almost non existent and unknown to everyone. Who/what made the first vegan become vegan?

I don't know if there's a book/website that has any good analysis on the phenomenon.

What/who do you think made it happen?

Ps: if there are some early vegans amongst you, what made you go vegan decades ago? How did you find that movement?