Manchester United were a bit lucky, the whole game was possessed by Arsenal, if Arsenal attack was as strong as Liverpool then the number of goals in that match would be more numbered than yesterday score line. Arsenal had no progressive attack, they focused on one part of the field which United was aware and capable of defending themselves, a more better performance from Arsenal would have given them the winner but they were unlucky to share points when they needed it the most.
Actually for this I think it's not about luck but strategy because looking at what happened in this match we can certainly see that even though for 90 minutes of the match Manchester United appeared defensive but seeing the quality of the attacks they did actually it was quite extraordinary and could even keep up with Arsenal even though in terms of possession they lost.
Nothing can really be considered lucky because Manchester United also managed to make some good things despite losing possession in the match that took place I don't feel that it is an aspect of a club being lucky if it gets a positive result because after all in matches it all depends on the game scheme not hoping for luck.
That can be a positive thing for Manchester United but not good enough for Arsenal because indirectly they are increasingly closing themselves out of the trophy competition considering the difference in points with Liverpool is too far.