Days before King Charles III was to be formally crowned in England, there was another coronation underway in Boston. Or at least that was the unmistakable vibe during Game 1 of the Boston Bruins' series against the Florida Panthers.

The 2022-23 Bruins were the most successful regular-season team in NHL history, setting new league records for wins (65) and points (135) in a single season. Even if you didn't believe they'd win the Stanley Cup, the Bruins' going on a playoff journey toward one felt like a certainty. Their first-round series against the Florida Panthers was like sitting through the previews before the real movie starts.

Until it wasn't.

The Panthers rallied from a 3-1 series deficit, and a 3-2 Game 7 deficit with one minute remaining in regulation, to eliminate the Bruins from the Stanley Cup playoffs on Sunday night. Carter Verhaeghe's goal 8:35 into overtime turned TD Garden into a silent mortuary where a championship inevitability was laid to rest.

"It hurts. You compete hard and battle all year for that," captain Patrice Bergeron said. "We're shocked and disappointed."

What went wrong? Here are five possible reasons the Boston Bruins became yet another regular-season titan that was toppled in the playoffs.