Because they can.

Because they really needed to get better than they already were.

Because being defending Super Bowl champions was not enough cachet as they embarked on their title defense.

Because their Hall of Fame-bound head coach and Hall of Fame-bound quarterback needed more help.

Because there’s a bare spot on a shelf in their lobby that actually doesn’t have a Lombardi Trophy on it.

That’s why the Patriots are signing receiver Antonio Brown.

While Patriots coach Bill Belichick, in his Monday conference call with reporters, continued to do this silly dance around the topic, declining to even acknowledge Brown, the troubled drama-queen receiver formerly of the Steelers and Raiders (well, kind of), everyone else around him in the organization has been speaking openly about New England’s newest reclamation project.

There was Patriots owner Robert Kraft gleefully informing NBC’s “Sunday Night Football’’ broadcaster Al Michaels that quarterback Tom Brady told him he was “a million percent in” on the team bringing Brown aboard.

Then there were Patriots players, in the locker room after New England’s thorough 33-3 dismantling of the Steelers, talking to reporters about the virtues of having such a playmaker like Brown on the team.

“It will be fun,” receiver Julian Edelman said to reporters. “He’s an explosive player, and we’re happy to have him. The more playmakers you have out there, the better things can go.”

Fellow receiver Josh Gordon, himself a Patriots reclamation project with his alcohol-related league suspensions, told reporters that his initial experience joining the Patriots, with their established, disciplined system, “was a culture shock.”

Gordon said as he “grew’’ in the Patriots “environment’’ and “knew this is the way it’s done here,’’ he “could either get with it or look for a transition somewhere else.”

“It’s tough, but if this is what you want to do, I think this is the best place to be,’’ Gordon said. “Antonio is going to have to figure out his way, just like everybody else has.”

Receiver Phillip Dorsett, in an interview with ESPN, said the Patriots offense with Brown added to it “can definitely be scary.”

“I just can’t wait for him to come in, and I can’t wait to work with him,” Dorsett said. “I know how hard of a worker he is. He’s always been a guy I’ve looked up to when it came to football. I mean, I used to watch his highlights in college before games.”

Brady, in an interview with Peter King’s “Football Morning in America,” sounded like he was taking a wait-and-see approach to Brown’s arrival.

“There was a lot of positive emotion when it happened,” Brady told King. “But you know, the teams I’ve been on, they go to work. Now we’ll add Antonio, and … there’s a lot to learn. The point is, it’s one thing to talk about, it’s another thing to go do it. Let’s go do it.”

Brady went on to say of the Brown signing that he doesn’t think the team “would make a decision like that if they doubt it’s going to work.”

So there it is: The NFL’s best team got better over the weekend while the other three teams in the AFC East, the Patriots’ supposed division rivals, looked like, well, like they always do: not even close to a threat to New England.

The Dolphins, in unabashed tank mode, showed that they gave up on the season before it started. The Jets looked the same as they’ve looked for the past eight seasons. And the Bills could barely beat the Jets.

So, all the Patriots’ addition of Brown does is make the AFC East — and the rest of the league for that matter — even more of a mismatch than it already was.