The Glazers have always been open to selling the club the past few years, especially when selling the club at its highest point with recent broadcast deals. Woodward has done a lot questionable things and the fact that the football structure has change recently under Woodward, which delegates roles to others that was not previously clear or even present, shows Woodward's decline of influence or final say.
He's always been a pawn and while good for the owners, he's been detrimental to the club since Fergie and Gill left. As much as the owners have hurt the club with the leveraged buyout and debt, they've still given the club ample amounts of cash or allowed a lot of cash be spent. It just hasn't been spent well enough over the years on the pitch or for the stadium as OT needs to be renovated in stages.
Ed Woodward resigning is good, but also can be bad. Who is to say that the next Vice Chairman and CEO isn't going to go on a power trip and make stupid decisions while the owners let them be? Either way, Vice Chairmans and CEOs always take their orders from shareholders and in this case, its the owners. Be happy, but be aware of what could happen with a questionable hire/replacement.