>>991613A lot of reasons.
Ame to a lot of people is the most relatable. She came from humble beginnings, gamer, her general lifestyle, her lack of any one specific major talant, etc. Yet she's also very hardworking despite also being very lazy. She never quits and keeps trying to do things her way until she can get them done. She also cares about her fans a lot, and she's both very comfortable and open about what she's thinking and feeling to them.
Also has to do with the fact that Hololive, and idol stuff were new to her and she embraced it and was inspired by it while still being herself. She's also incredible supportive of everyone in Hololive. This also makes her even more relatable to her fans who also went through that same experience.
She also...just has this way about her that...just makes you love her. Her calming and soothing voice, the way she teases you while still being sweet. She just feels really...real and honest.
Probably didn't explain it as clearly as I could but I feel like you get the idea.