The Bengals were holding onto a slim 14-13 lead. The Buccaneers were driving with under a minute left. They'd pushed the ball into field goal range:
Then, after that play, Lewis threw a challenge flag. But wait! Coaches aren't allowed to challenge plays with under two minutes left. That's the job of the review booth. The Bengals were charged a timeout, and without getting the play they wanted reviewed. What was Marvin Lewis thinking?
In fact, it was Lewis' seemingly illegal and mindless decision that ended up saving the Bengals. Over the course of the timeout, the replay official decided to review the play -- previously, they weren't going to, and the Bucs were getting up to the line of scrimmage to snap quickly. The Buccaneers had run the play with 12 men on the field.
Previously, this would not have worked. The NFL famously had a widely despised rule saying that if a coach challenged a play he was not allowed to challenge, then that play could not be reviewed -- even if the league's replay officials would have otherwise reviewed it. This cost the Detroit Lions a game a few years ago.
The rule was considered one of the league's worst, since the NFL was essentially admitting it would overlook the correct call on certain plays to spite coaches for making a bad spur-of-the-moment decision. However, this rule was overturned in 2013 -- the Jim Schwartz rule, it was called at the time.
So the refs reviewed the play and realized that instead of a 21-yard gain giving the Buccaneers the ball at the 20-yard line, they should be charged with having 12 men on the field and face 2nd-and-20 at the 46 yard line. They failed to pick up a first down and the Bengals got the 14-13 win.
Is it a bit messed up that Lewis intentionally flouted the rules a bit to get his team a favorable situation? Meh, maybe a tad. But the alternative was the Buccaneers getting a potentially game-winning play by using more people than they were allowed to use. Lewis did what he was allowed to do to ensure the play was called properly, and his team will walk away with a win because of it. He could probably have gotten the same result by calling a timeout -- which is totally allowed -- but by doing this, he also made it clear that he wanted the refs to look at something.
(Maybe coaches should just be allowed to call challenges whenever, so long as they have one remaining, and we can be done with this weird loophole?)