I wrote a month ago that the Red Sox were a .500 team because they were first in runs scored, with only few teams in their range, and worst in runs allowed with only a few teams in their range. I maintained that there is no need to discuss their hitters or their attitude or their character, or whatever. They were letting in too many runs, they weren't going anywhere.
For May, they are 6th or so in runs scored, with a few others pretty close as well. However, they are in the middle of the pack in runs allowed, a substantial improvement. They are only one game over .500, BTW. And the lineup contains names I am completely unfamiliar with.
My guess: solid but not spectacular pitching, plus either injuries to position players or young hotshots coming back to earth. Nothing to see here: move along. This team is only going somewhere if it noses into the playoffs and has fewer injuries than the other remaining teams/