Chapel isn't good for Fool's Gold in mirrors because you are trying to win the FG split, and chapel slows that down - you have to spend a turn buying it, and then you are not trashing much with it (which defeats the point) or spending more turns trashing - all of which could have been FG. However, in non-mirrors, or to be more specific, when your opponent is not going for FG (say they're going for a treasureless deck - this is reasonably likely considering the presence of chapel on board), then chapel is really good for fool's gold, because it helps them connect a lot. So, you can't just make such a broad statement as 'fool's gold "dislikes chapel"', because it's only situationally true.