He was Vince's right hand person basically. Him and Patterson was basically Vince's key guys under him who he trusted the most there. Its a big deal to see him go as either things are hurting worse than we imagined or perhaps Bisco's health isn't the best for this role anymore (he's 73 years old).
I do have to say this for Vince McMahon and all. If he is loyal to you , you will work a long time there. Gerald Brisco and his brother helped Vince get Georgia then and he seemingly was very good to them. He kept them employed for years even when he didn't have to.