First, I do not believe Bartomeu is willing to accept any exit unless he can have control of the narrative/terms of said exit.
Two, I am on the fence as to whether Bartomeu believed Messi would follow through on a threatened exit or even wonder whether this was not always his goal anyway - I just think the timing (Esp. due to COVID) probably was not something he saw coming.
Three, I do not believe Bartomeu cares whether Leo is happy now or not - now it is about saving his remaining mandate along with a continuity candidate
Four, the money matters for Bartomeu - particularly because the club is paralyzed on multiple fronts without it or Messi, there is a domino effect there that even Barto & his stooges cannot spin into gold. Ideally for Barto he'd get a high fee + player exchange along with a public Messi exit ceremony where he can recapture some credibility although I doubt very much he'll get the latter.