I have to be honest, I was not happy with the ending of this game. I would love to maybe have a more clear interpretation of what actually happened. My main question is - why did Tidus have to disappear at the end? And what was the purpose of Dream Zanarkand in the first place?

I guess I missed the entire point of the story in that sense, and it's been a while since I played it so I'm not exactly sharp on the story but I would love some clarification on why the fayth felt this specifically needed to happen. To deal with Sin? But Sin keeps showing up! Somebody help the questions in my head!