The move for the Vikings ended up saving them $9.99 million on the salary cap in 2023. O’Neill was the ideal candidate for this to happen, as his contract is likely to see its end after the 2027 season.
Making this move right before the season is done to give a team salary cap space for in season moves. Per game roster bonuses don’t hit the salary cap until they are earned, which need salary cap space. It’s the same thing that the Vikings dealt with last season with Za’Darius Smith.
It’s not likely that the Vikings made this move to sign someone from the outside, but it’s also not an impossibility.