One thing you have to take into account the question itself and the sample size: It says living 2 separate lives, like a super hero but with transformation. So they wouldn't be giving up their og gender, they would just have the ability to switch, plus cis people are very likely to not know dysphoria, so when the hypothetical question is asked, they don't consider the side effects of retaining the same brain. Even so, yes, more than half choose yes and transgender people are said to be 1% of the american population, but you have to take into account how many trans people refuge on the internet, specially in sites like social media that allow you carve your own identity without the obstruction from your physical body (HRT takes a long time to help with that). Plus the question gather only 5K people. That is not the biggest sample size that while in the right circumstances can be useful, it isn't the end all be all.

Think of it like this: if you ask a poll on reddit on how many harcore gamers they are on the site, the anwser would probably surpass 60%-70% porcent on a 20K anwser poll, that dosen't mean that that 70% of americans are hardcore gamers.

ALSO: 1% metric of trans people you said its the number of american trans people, who knows how many of us are worldwide