There are some big differences between Abramovic and Glazer. The first is a billionnaire in his own right (ignoring for a moment where the money came from) and the latter is only a millionnaire who is borrowing significant amounts to support the purchase. I can quite believe he will invest in the club but expect him to try and pay off his debts first so there may be some short-term pain before some longer-term gain.
Chelsea fans may be happy now but if Abramovic ever decides to call it quits it could cripple the club if the underlying business is relying too heavily on his money.
Either way we have two owners who know/knew little about football and the 'eggs in one basket' analogy could come home to roost for either one day.