In Infinity we end up doing a lot *before* the events of Marathon 2. Things like, damaging the Mnr Dam, flooding the area we later(previously?) explore on Charon Doesn't Make Change.
More notably, both Infinity and M2 end with the trih xeem being deployed, Lhwon's star going nova, and an aparent total lack of Wrckanter. Maybe the nova at the end of M2 passed with barely a mention *because* we were also simultaneously on a space station hidden elsewhere in the system powering up the magic wrk-restrainer.