There's a world of difference between a "bad owner" and one who is attempting to kill, literally as per your words, a football club.
Mike Ashley didn't get to where he is in the world, and become as wealthy as he has, by intentionally devaluing or taking-to-zero the assets he owns. I certainly...
£224m according to this...
https://www.northstandchat.com/showthread.php?372552-Albion-valued-at-%A3224-million
....which valued Newcastle at £383m, so not too far away from the reported value of this deal.