I always noted last year was peculiar in that the team won 93 games without anybody actually playing well. I mean - there were no dumpster fire seasons, but there were no "leaps", no crazy outlier seasons (except for Moreland to a certain degree). Between their health problems and "non-outstandingness", the 93 games felt at times like really the worst this team could have done. A LOT of their improvement was going to come from just their own guys playing better.
So whaddya know? Martinez has been a crucial signing for lengthening the lineup - he has been everything anyone could have asked for. But instead we get major leaps by Betts, Benintendi, Bogaerts at the same time. Moreland/Pierce have been a super effective 1B combination, and they have been more than good enough to compensate for real struggles at the bottom of the lineup. Even Devers - while struggling - has not been that bad, certainly nothing holding much back with significant potential to turn some stuff around.
It is tempting to give Cora credit for this - but probably a little unfair. That said, the seasons these guys are having is why having great young talent is awesome. It is silly not to expect some regression - but these are premium talents, and a good chunk of this is really who they are.