Well, there are a few reasons at work.
1. The Orioles don't suck.
2. Bloom took a bunch of die rolls last season that worked - and the die rolls this season have not been as successful, particularly in 1B/RF, positions where teams NEED offense
3. They brought in one of the top free agents in the entire class! He just has been bad. Yes, he has been excellent defensively, but "great defensive 2B who is a sub .300 OBP" is absolutely not a victory for what they asked out of Trevor Story
4. Health with Kike and the starters. And that is allowing for the possibility Kike was going to turn into a pumpkin at the plate.
5. The Chris Sale Experience
Ironically, his starting die rolls were not that bad. Like, Wacha has been terrific - his injury was a huge loss for this team. Rich Hill was less so, but it's not like the Garrett Richards experience was amazing.
The Red Sox defense has been better than last year - but team has struck out fewer batters and (relatively, not absolutely) have given up more homeruns. And so there has been a drop in FIP.
Here is the thing. When ownership decided to make the Betts deal a Price salary dump (their prerogative, it makes sense) - the chance to get an All-Star talent from that deal went down the tubes. (though Downs I think will be a solid big league something) The Next Great Star in the system is likely 2 years away at minimum. (Mayer and Bleis are the names to watch, though their sandwich pick this year has some serious tools)
The team does have a chance to be pretty good next year - a lot of money they can move around. But the range of outcomes is wide.