It was an opportunity squandered. While there are no guarantees in life or football, no one will be surprised if/when KC wins the Super Bowl. It's already inevitable to think, "that could have been us."
Consider:
1) It's been suggested that the Bills should have squibbed or blooped the last kickoff before OT. The counter-argument of course is the Music City Miracle or even a straight-forward kickoff return for a TD. That decision is at least debatable.
2) However regarding the last 13 seconds from scrimmage, Romo made the legit point that the Bills needn't rush 4 because with 13 seconds left Mahomes was gonna throw quickly before the pressure arrived anyways. So why didn't the Bills simply drop 11 into coverage? Time was the pass rusher (one Mississippi, two Mississippi, etc). You could double team their top 3 receivers and still have 5 players dropping into zone coverage.
3) OR: why not play press coverage and commit one holding or illegal contact penalty (committing two is a "palapably unfair act" and would result in a 15 yard penalty and no time elapsed)? Regardless of accepting or declining the 5 or 10 yard penalties, time would have elapsed. While a game cannot end on a defensive penalty the Bills would have at least been able to take time off the clock without giving up much yardage.
4) And again, why were the Bills guarding the sidelines when KC had 3 timeouts remaining???
In summary, the Bills could not have strategized the final 13 seconds any worse than they did. While that's on McDermott (a longtime DC) it's a failure of both he and Frazier and the whole defensive coaching staff.
No one on the defensive staff had a better idea than what they ended up doing?
I still love and support McDermott but this one's on him.