The first Marvel Avengers Alliance game was a huge hit and that was the reason why Disney felt that a sequel would work. However, the sequel did not do as well as the first game and Disney ended up axing both these games altogether a few months ago.
According to Disney, the reason why they decided to kill off the games was so that they can put their effort and time into something better. We still do not know what Disney has in mind but some fans think that it might actually be a new Marvel Avengers Alliance game.
Fans were pretty unhappy with the decision but not because they were going to missed the game but some fans were still unhappy about the fact that Disney killed of Disney Infiniti. There were talks about Disney possibly thinking about killing off all their games and focus on licensing but that is just one of the many rumors out there.