Because he nearly ran the club out of existence. We're staring down the barrell of a 12 point deduction for breaching the rules, likely a nailed on relegation sentence. If we go down in our current state administration or worse is essentially what will happen.
He lied too and about supporters frequently purely to save his own skin. It was only over largely relatively small things (selling players, club appointments, stadium moves, etc) until January this year. That's when he overstepped the line to the point that I and many others no longer had any respect for him as a man, forget his role as a football club chairman. Accusing his critics of assaulting DBB, in what has been shown since to almost certainly be a case of fake news, all to try and slander those who were trying to pressure him into stepping down. Disgusting conduct and a window in his soul.
He undoubtedly did good in his life, but none of that stuff is the concern of the average match-going Evertonian who wants the club to take itself and to be taken seriously as a sporting institution. If people want to honour him then do it in a different setting, not right before the club he caused catastrophic damage too is about to play.