The Moroccan arrived from Bayern Munich along with Dutch defender Matthijs De Ligt.
Mazraoui has become a mainstay at right back for United, with Diogo Dalot switching to left back.
He told reporters: “If you compare both of them, you cannot say one is bigger than the other. Maybe internationally speaking, Manchester United is probably bigger than Bayern so that’s for sure one of the reasons.
“The other reason is that I felt at that time, last summer, after two seasons at Bayern, I needed and wanted another step based on a lot of reasons. I felt OK there but I had a feeling that I can feel better and more comfortable somewhere else. That’s why I eventually chose to change clubs and that’s where Manchester United came in. I don’t really think I have to explain why I chose such a decision.”
On playing for Ten Hag, he added: “Of course it’s a big factor. Always if you decide to go to another club, you have to decide if the manager and his way of seeing football fits into your way of playing football. I knew him already, I knew his way of seeing the game and his style really fits into how I play and that’s really a big factor.
“That you work beforehand with him also makes it easier. I knew what he expected from me and he knows it from my side as well. Seeing those things makes it easier, but eventually it’s what I said, it was not the only factor why I came to this big club.”
On his relationship with De Ligt, he added: “Of course, I think that’s also one of the big things, not just him but already I knew others here to settle down easier. It’s tough to come to a new club with new players and new people but the moment you feel comfortable is the moment you play better. Because I knew some players here and I came together with Matthijs, which makes life easier.”