I've seen a number of videos on Twitter/Tiktok where trans people complain that cis men/women won't date trans people and they'll use that as a basis to call them transphobic. The problem is these people have been conditioned to believe being a trans woman is no different than being a regular women, and they say things like these cis people shouldn't be afraid of a "feminine penis" and such things. It even feels crazy to type that last bit out. These poor people have been coddled into believing a lie for so long when they should have been getting help.
It is mental illness. I'm only partway through this video, but there's some interesting points made. Trans people are 4 times more likely to have a psychiatric disorder compared to a control group, with 10,000 trans people being used for the study and 53 million in the control group. Often times the issue stems from childhood, I've seen it personally with my niece. She was abused as a toddler by her own father and it left her confused and torn on her own gender and sexuality for a long time. It's tragic, and after an abusive relationship in high school she somehow flipped the script and found a healthy rewarding relationship with a straight guy and she considers herself a girl today. There are things she'll probably never get over. She's been through so much, and it makes me sad to think how many others have been through similar situations and the damage it's caused.