Males (nonbinairy?) going on estrogen to then get topsurgery???

I've seen this in two different subs now, but I do not feel like asking in any other sub bc then It'll just be bombarded with threats lol. But basically the title... How? Why? What? Why would you as a male go on estrogen to then get topsurgery because you don't want boobs? This doesn't make sense to me, as a trans guy this makes my head explode. Can anyone explain (English isn't my first language btw)