Diame, 25, is certain he made the right choice, swapping a half-empty DW Stadium for a packed Upton Park.
He said: "I was at Wigan for three years and they offered me an extension for three more. But I was a little bit tired of spending the last day of the season trying to stay up every year.
"We played good football there and I enjoyed it. But in my mind it was very difficult coming home from every game thinking, 'Oh, we could go down'. I needed this chance, this challenge.
"I wanted to come somewhere I could be more successful. That's why I didn't accept Wigan's offer.
"I talked with West Ham and they told me about the people they were going to sign. When you come from the Championship, you don't want to go back down.
"I knew they were going to make their mark on the Premier League. I think I made a good choice because I'm very happy at this club.
"I see a lot of people behind the club. That shows me it's a big club. There are a lot of fans in the stadium. It's not like Wigan. They had fans too, but not like they do here.
"When we started the season with Wigan we started to lose games 4-0, 5-0. We had no security. Here we are closer to a clean sheet in every game."