If the debts are written off, if the parachute payments plus the extra investment cover the losses and give him a wad to spend, if the players he buys work out, if he can get top players to drop to League 1, if the players already there suddenly stop being useless twats, if it all clicks, if there aren't two other teams that somehow do better next year, if he doesn't hit one of those inexplicable "on paper they should be top, why are they in the bottom half" seasons, if his approach works again, yeah, then they'll walk it.
Our situation - if the budget is the same as last year we'll do massively worse than last year? That doesn't make sense. The team as is has shown it can perform, why would Wilder believe he can't do it again?
His options aren't so straightforward as you believe. The choice isn't obvious. Sunderland could get it together, they could also crash and burn. We could also get it together, things are changing on the ownership front and nobody knows where that will lead.
As I've said before, the only reason he would be tempted is if he has an enormous pay day, presuming that is the sum of his ambition.