I think you're interpreting "trust" mostly in terms of "this person will tell me true things", but telling you the truth is pretty far down the list of what therapists do. "Truth" is often not even well-defined when it comes to your internal mental state.

Most of the truths that you hear in a good therapy session will come out of your own mouth. You just didn't know they were in there until the therapist guided you to them.

Try to think of "trust" more in terms of safety. With a good therapist, you can trust that if you share your truth with them, with all it's ugly dark aspects, that they will not use that knowledge to harm you.