I have strong suspicion that one of the professors regardless of the professional relationship we had was not very nice in the recommendation letter. This is after knowing him at a personal level and how perfectionist and judgmental he is of other people. But let's not get into why I chose him to write my recommendation letter, you can assume I had my reasons. I got into the master's program I wanted which is one of the top in the US.
But that was the only program I got into while other programs ranked much lower declined me. My grades were good and my record was good the two other recommendation letters were good for a fact, so that only leaves me to assume that this top college did not weigh in so heavily on his recommendation letter to make their decision.
But all this is speculative, my question and concern is, should I let him know that I got into the program I wanted regardless? I want to do this as a courtesy and a thank you message. My fear is that he might go as far as approach the committee and ask for my admission to be re-evaluated. Or bad-mouth me to colleagues in that university if he knows I am attending.