Villa were able to score a quick goal... I hope that before the end of the match Arsenal will also be able to score... Judging by the game it seems to me that it is not yet a fact that Villa will be the winner... But if it happens, Liverpool will become the new leader...
It looks like neither Manchester City nor Arsenal will be the top contenders at this moment, but Aston Villa and Liverpool. Although indeed, there is still plenty of time in this match for Arsenal to turn things around but ya, considering the success of Aston Villa beating Manchester City. So ya, at least at this moment I am sure that Aston Villa will not be defeated by Arsenal, because so far this season the fact is that Aston Villa still has very good results for home matches. In the previous match Aston Villa managed to beat Manchester City and in this match, again and again it looks like Aston Villa will also beat another top team and that is Arsenal.
Manchester City and Arsenal both lost against Aston Villa. And after defeating Arsenal, the Arsenal team is now third in the points table. Aston Villa is now only 2 points behind Liverpool who are at the top of the points table. Now I think Liverpool, Arsenal, and Manchester City as well as Aston Villa are fighting for the title this season. Aston Villa's performance is very stable. This team is quite strong forward. They can score a lot of goals. This is why the Aston Villa team is able to get good results in every match.
Aston Villa is now in its best form and this is better than last season I think when they could only rotate in 7th place in the table of standings to finish in that position also at the end of the season, basically it is not easy and even very difficult to be able to get the full three points for some medium teams when dealing with Manchester City or Arsenal, but Aston Villa can prove by breaking some doubts that arise with that evidence.
I see not only Aston Villa but Liverpool also has a pretty good change, it looks like this season will be much more interesting than previous seasons as we know that usually only Manchester City and Arsenal are always competing tightly in the top area. On the other hand Manchester City is experiencing a significant decline, I don't know what went wrong there, but certainly it seems to be true as you said that the title race this season is not only for Manchester City and Arsenal but Aston Villa and Liverpool are also competing in the hunt. So we'll see who is stronger until the time comes.