I noticed someone was using my account on web player yesterday. My music kept skipping to the next song, and I kept being prompted to "keep listening on webplayer or switch to this iPhone". I went to my account settings and signed out of all devices, which solved the main problem.

I checked my recent listening history to see if I could find out who was using my account, since it's possible I had left it signed in on a friend's computer. The 4 playlists that this person was listening to seemed strange to me because they had all the same songs on them, and were followed by 1000-2000 people. However, when I clicked the names of the people who supposedly made these playlists, they only had two playlists and they both had the same songs on them. 

It just seems weird to me that these playlists would have so many followers when it's clear that the user isn't active. Was my account hijacked in order to take part in some sort of plan to falsely increase plays for these songs to give the artists more money/higher standing in the music charts?

Screenshots attached: