@Tattie I'm a cis guy. I've always been in favor of trans rights since I learned trans people were a thing, but I did spend a number of years not really getting why someone would be trans.
Then one day I just had the thought, "What if I woke up tomorrow with a female body?" And after the obvious jokes that immediately came to mind, I actually thought about being stuck in the wrong body, unable to get back, and I had to stop because I almost gave myself a panic attack.
I'm an on-again-off-again recreational author, so I frequently find myself in unusual thought experiments. Which is to say, I hadn't intended to have a moment of profound empathy for trans people, but as soon as I calmed down I thought, Oh, this must be how a lot of trans people feel all time.
All of that to say: I see you. It's real. I think most cis people, if they put just a few minutes into the activity, would be forced to admit that if they were suddenly body swapped, they'd be desperate to get back to their correct body. Most cis people just never seriously confront the thought.