It's a reasonable question, but I don't think anyone could have watched that game and concluded anything other than at no point did Man City bust a gut and could've done more if they'd wanted to. We'll probably never know for sure why they chose not to.
I think it was more down to City having a below par day rather than us giving them a "hard game" TBH, but we don't have to agree on that viewpoint, of course.
Probably the best scoreline we could've envisaged before the game. City played well below par for them, so have to keep that in perspective, but we've had worse afternoons....