I'm not truly sure which one of the two reasons came up first, so I'll say them both...
Once I saw an Italian Youtube channel that speaks about video games that had made a few recension about games labelled as "impossible", showing them one after another, and in between them there was Touhou Project as well. I had only heard about it a few times on the net before that time, but what he showed looked really interesting and challenging, so I decided to give it a try sooner or later.
Then I can't remember if this other "triggering event" has happened before or later, however, time ago I used to play Osu a lot, as a few friends found out about it and got me into it as well. While downloading songs I eventually ended up on Japanese tracks, and one of those was "Tsurupettan" by Silver Forest. The song caught me at the first time playing the track, so I moved it onto my mobile. Curious about the whereabouts of the song and creators, I found out about Silver Forest and that it was a re-arrangement of a Touhou Project song. After listening to a few other songs I couldn't take it any longer and went to find a download for one of the games, ending up with Touhou 1, Touhou 2 and Touhou 8 (which I had already tried to download a few months after it was released, but at that time my connection probably failed on me and I found again just a touhou-08-IN.part file in my computer), playing them and literally falling in love with Imperishable Night. From that moment I started downloading fan made games, official games and their spin offs, etc, etc. Well, this is how I got into Touhou, but my dream is still this: Be able to find somewhere to buy the original copies of the games so that I can contribute to ZUN and prove my love for this series.