I also attended it for grad school only. Nobody was even close to failing out. I don't think MIT did a lot of grade inflation and generally regard it as a very strong academic institution.

That's not incompatible with weaker students being able to pass by with lower grades. Getting bare minimum grades just isn't that difficult.

edit: teammwork also seemed to be strongly encouraged. It wasn't a place that wanted you to fail. It wanted to help you succeed, which is by all means a good thing.