Marvel Now megashipped a lot of books though. Fraction was really writing a 28-issue series in two books over the course of a year. You can only take that kind of breakneck pace for so long.
Avengers has already shipped more than 20 issues in Marvel Now, and New Avengers another dozen as of this week (plus Infinity). Superior Spider-Man has already shipped 20 issues this year (plus Avenging and Team-Up). It's craziness.
It's no surprise they have to rotate creative teams at this point.