As I said, this doesn't make sense even within the modern American right. Bud Light has been loudly supporting trans rights for years now with no backlash I can remember. Why did associating with a transgender person for a single video result in more outrage than years of deliberate political activism?

It's a random social media outburst. People latched on to one trivial event because that's what happens on the Internet. There is no rational explanation.