I don't think you are posting in good faith, Places. There seems to be a real (unsubtle) attempt to lure other posters into making the mistake of using terminology that, apparently, isn't allowed on MN (or perhaps just on this particular part of MN). That's rather spiteful and mean, if you don't mind me saying so.
However, I'll answer your questions, re why are people trans - my views.
I think people believe in gender ideology for many reasons. Some are genuinely dysphoric about their own biological and genetic makeup, and I assume there's probably many actual "reasons" for that which I also assume they explore with therapeutic services before they embark on their transition. I think other reasons will vary, from social contagion all the way to trying to escape previous abuses and into those who enjoy various sexual fetishes. Reasons are, I imagine, as individual as, well, individuals. There may well be many people who have multiple factors combining to create their belief that they somehow will be happier or more content pretending to be a different organism from that which they are. I'm also sure there's a proportion that just enjoy having some sort of "power" over others - the power to compel speech, etc etc. As to how those numbers break down, you'll have to do your own research on that.
The cut and thrust of it is how far do we expect the rest of society to bend in order to accommodate these different individuals and their individual needs and wants. I propose that some individuals will be easier to accommodate than others, that some accommodations will be seamless and natural and the blend will be easy. Other accommodations will be jaggy and cause grazes, scrapes and cuts, leaving scars and scabs on other parts of society, in other words, these accommodations will cause some harm to others. Some accommodations will cause a lot of harm to others, depending on circumstances.
I don't personally believe that other people should be asked (or rather, told) to make sacrifices to their own wellbeing (mental, physical, emotional) and lifestyles in order to accommodate another individual's needs and wants.
I expect the thread has moved on since I started to type this, but it was asked, and I've answered as best I can.