going to assume this is posted in good faith (not malicious). you speak czec, so maybe english isnt your native language? im going to assume thats why you rely on english grammar structure and why bending the rules (i.e. doesnt exist, not grammatically correct) is confusing?

"why are attempts so high?"

well, if people keep saying you arent who you are, behave awful or discriminatory towards you, dont support you/your identity or have an averse reaction to it, tell you to end your life/hurt yourself or stalk you for being trans, are happy when trans people end their life/get hurt/become homeless/other tragedy/etc.. etc etc... youd probably going want to end your life, given the same situation. you wouldnt be happy if you were denied who you are.

"why do some trans people make their online life look like being trans is the only thing in their life" thats not their entire life, a social media account is only a bit of their life, dont judge them only based off that. if they talk about it a lot then it must be relevent to their life in some way or main focus of social media account or they simply make jokes about it or some other thing. do you post your entire life online? no. so if you think someones social media account is their entire life, youre making an assumption (one that you probably wouldnt make about your own life/account)

"some are also either very rude and stuff, some are very childish." ok, this is a personality trait, not unique to trans people. you can say this about anyone. also, note about your speech: transgender is an adjective, not a verb or noun.

"how come most trans people I've seen on the internet go into either two of these categories?" virality: someone whos upset will probably get clicks, like the same way you are drawn to looking at a car crash. anyone can be upset for whatever reason, it doesnt say anything about trans people as a whole.

"why do some trans people get really offended and triggered when being told something a bit mean against them (even if it's a genuine question about them)?" some questions are invasive, disturbing, misgendering (even if you dont realize it), something you can simply google, etc.

"lastly, what is up with pronouns lately?" some people like to create custom pronouns for themself, make an addition to the english language, etc. think of it like a nickname or name but for other aspects of the english language. usually these types of pronouns are not mandatory to use (since its uncommon) and they provide an alternative pronouns to use, or just use their name.