The play selection there for the Bengals didn't make a lot of sense, especially 2nd down. Can't blame the crowd for booing.
Nothing, really. People just mythologized what he did last year. His numbers this year are pretty similar to last year, both rushing and passing. And they are doing the same thing as last year: losing lots of close games. Right now, they are 1-5 with 4 one-possession losses. Last year, they were 1-5 with 4 one-possession losses. Newton's throwing and rushing is basically the same as last year - his yardage per pass and rush attempt are a tiny bit higher. His total passing is a little bit lower (fewer attempts). His rushing yards per game are the same. His INT pace is the same. His TD pace is a tiny bit lower, though if he had 2 more total TDs, it would be the same. Basically, he hasn't really gotten notably worse - he just hasn't gotten any better.
Chargers placed K Nate Kaeding on IR. However, his time in SD is reportedly up, as they will release him as soon as he can pass a physical. Redskins WR Pierre Garcon reportedly has a torn tendon in his foot. MJD is out this week with a foot injury, almost assuredly longer. Brady Quinn replaces Matt Cassel as Chiefs starting QB. Charles Woodson has a broken collarbone and is out 6 weeks. Panthers CB Chris Gamble was placed on IR with a shoulder injury.
You're not accounting for the Fantasy Football angle. His rushing TDs are down and the Fantasy community is a big part in framing the discussions surrounding a players performance these days.