Both the MAC and the NAC have their strong points. The MAC's good because it has more judges/competitors and it's generally more popular than the NAC, and the NAC's good because the judges review the Top 8, and of course the NAC is monthly whereas the MAC happens once every 2 months and doesn't occur while the NGADM's running. So I wouldn't say that there's no point for the NAC to continue with the MAC running, even though it seems to be that way since in this month there happened to be a similar theme in both competitions.
However running a competition is a lot of work, and looking at it realistically Chron runs the thing, organises the judges, is a judge himself AND takes care of the forum sig prizes, every month. That's a hell of a lot to do for just one person; even for two it's a hefty workload.