It is all about offensive efficiency. With the raw numbers, DET's offense looks relatively the same, but it is way different than last year.
DET was a +0.15 EPA/Play last year,+0.25 per pass and +0.04 per rush.
This season? DET is down to +0.05 EPA/P (-0.10), +0.12 per pass (-0.13) and -0.06 per rush (-0.10).
So their passing efficiency got cut in half, their rushing went from a net positive to a net negative, resulting in a 66% relative drop in overall offensive efficiency.
3rd Downs? They went from 47.6% to 38.3%, a 9% drop.
% of scoring drives 51.6% to 43.8%, an 8% drop.
The Bears on the other hand went from -0.13 to +0.03 for EPA/P (+0.16), -0.15 to +0.02 per pass (+0.17), and -0.09 to +0.05 per rush (+0.14).
The Bears on 3rd Downs: 32.9% to 43.1%, a 10% gain.
% of scoring drives 29.8% to 44.6%, a 15% gain.
So the raw stats are still there, but the efficiency of the offense is now with the Bears.
It seems like they are running relatively the same offense, but every game, and every season, they will be that much more removed from it. I would expect some of the raw numbers to start falling off next year. With the easier schedule, that roster can still compete, but I don't see them being a juggernaut anymore. Goff has a $69M cap hit next season, St. Brown's is $33M. So between those two players, over $100M. Sewell is $28M and McNeill is $29M, that's another $57M, so $160M in 4 players, that's crazy.