It could be that the people that you have experience with were not experienced in gender issues. After all, you don’t see a dermatologist for an orthopedic problem.
There are a number of reasons why trans people see therapists. One of the more common reasons is to understand their situation well enough so that they decide on a course of action. When dealing with life-changing decisions, there can be significant Approach-Avoidance conflicts. Beyond the process of transition, other things come into play such as dealing with with family issues, employment issues, resources for employers (not every HR department has some idea of how to work with trans people), deciding upon transitioning in place or start with a different employer after transition and other issues. Also, while detransitioning is rare, it does happen. That makes me wonder if they didn’t game the system in some way or worked with a therapist of lesser experience regarding gender issues.