A former teacher sent me a friend request on Facebook. Why did he only send one to me?

Anonymous
We are both musicians (him 36 and me 18) so probably that is why he sent me this request, but there were other students who were musicians yet he only sent me.
My friends sent him a friend request and he didn't accept them so I didn't bother to send him one (because most of the teachers told us that if we send them a request after we graduate they will accept, but they won't send one themselves.) a year and a half after I graduate… He sends me a request and a month afterwards he tells me to join a prayer group and play music with him once a month (he invited me in October and I could go in February).

When he heard me play he said that he really enjoyed playing with me and then he told me to play with him and a violinist at a funeral. I think that he sent me a request because he saw some kind of potential in me.
The thing that worries me slightly is that in school, students used to tease me (and eventually bullying me) because I was his favourite apparently and he was a bit too friendly. When I spoke to a teacher about the bullying, she immediately know to who i was referring to. My friend sees it strange that a former teacher sends a request only to me that is why I am posting this now because we were talking today and she said that it is a bit odd... Teacher sending a friend request to a student. I honestly always thought of him as someone to look up to and that I admire as a musician, inti fact, i did accept his friend request. What do you think?
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When I say "his favourite" meaning, he constantly teased me, he picked me for everything, always came up to me to talk to me in the mornings, he also once called me from the other side of the corridor to check if everything was prepared for the late morning mass, and then he invited me in this small room (it was like 4m by 4m length and width) to help him measure the walls and he closed the Door... i was 14 at the time and it felt really awkward being in that Small room along with him.
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He used to flush Red when seeing me and would always join in a group conversation (he used to do this with everyone, but..) each time he came next to me in the circle. There were a few months where in the mornings he would always look at me and say 'Good morning :)' every day and once i was so tired that I didn't look up and just started still looking downwards thinking about how much i wieħed staying in bed instead of going to school and I remember thinking to myself "He will pass by soon..
A former teacher sent me a friend request on Facebook. Why did he only send one to me?
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