Ridiculously long and complicated interview process, which included a project that took many hours to complete.
Trevor is very concerned with cultural fit, so apparently even if you have the required (and more) experience, if you don't fit culturally, they won't be interested.
The interview process is most likely indicative of their complicated culture. I assume if you're a person who likes to get work done in a timely manner, you would not like working for The Trevor Project.
I started interviewing in April and didn't even get through the whole process when I was rejected in June.