Arsenal were sloppy and gave Chelsea a goal, I think it has become a routine for Arsenal to concede at least a goal even in games they have full domination and last night was no exception, they lost focus as usual and gave Chelsea a good chance and Noni Madueke was smart enough to capitalize on the opportunity to get his first EPL goal for Chelsea.
Playing at home and dominating in a match is very common for Arsenal, especially what Arsenal are facing is a rather weak team this season, namely Chelsea. And conceding one goal also doesn't matter much for Arsenal if their closest rivals can now win all their remaining games this season. Even if Arsenal's closest rivals have lost once again in the remaining matches this season, Arsenal will also not get a championship trophy this season even though they are able to win all the remaining matches.