The Chargers have the 27th worst defense in points allowed (PPD), that's the biggest reason they're 2-2. Offensively they're 5th in scoring... it's the defense.
The Bengal's D isn't as bad but they're 19th in points allowed so they've fallen off from past years. The bigger problem has been their offensive line finally got Burrow too injured to move around... and if he can't run for his life behind that porous offensive line he is screwed. Their offense is ranked 29th in scoring but Burrow is starting to get healthy.
The Pats D is ranked 10th in points allowed (PPD), the majority of points this team has given up were pick sixes and fumble scoop and scores caused by Mac Jones. Since week two our offensive line also got healthier and they've let up half as many sacks in the past three games than they allowed in the first two. Mac has imploded.
With great QB to start this season they would be in a much better place. The QB position is the biggest problem on this team.