I think it's partially a side effect of spewing hate on a secondary account so their main one isn't at risk of getting banned, but it is pretty funny and sad how 9 times out of 10 when you click a transphobe's account (to block them) you can look at their posts and it turns out... This is all they do. They just hate.
You never click their blog and it goes like Zelda fanart, some cool song, cute cats, I hate trans people, some reblogged joke about "what do you call an armadillo who wants to be a deer?", gifset from yellow jackets.
Nope. Just hate. Everything they post or reblog is about their hate.
And they're either doing a secondary account for hate-only, or even worse: this is their only hobby. This is what they're here for. This is all they're here for.
It's a little funny, and a lot sad.