I left all my fandoms except for MLP, which is very new to me.
The reason I left various fandoms (Star Wars, Transformers, Pokemon) is because I found many aspect of their community's toxic. I still enjoy the series, but as far as participating in the fandom community I don't bother. Too hostile and silly.
That seems to be a good thing about MLP, the fandom fans I've encountered so far have been very chill and cool.
But to answer the question; MLP - I watched it one day when I was bored. Haven't looked back.