There are significantly fewer humans living in close contact with livestock in which a zoonotic virus could be transmitted. I'm skeptical that there has been a net increase. It's possible but I haven't seen any reliable evidence one way or the other.

But there are significantly more amounts of livestock in contact with those fewer humans.

Think of it this way: more total numbers = more opportunities for viruses to grow or mutate = more chances for runaway or novel infections. Runaway infections are dealt with fairly well by government entities. Novel infections... might be harder to discover because they're, well, novel.