Does anyone really care whose fault it is? Don't you just want your money?
Of course it's a Disney's issue, regardless of who the banking partner is! Disney picked Chase! And since Chase isn't reporting any huge online outages, I don't think this is a Chase issue anyway. As others have said, it would be unprecedented for a bank, particularly a bank the size of Chase, to have an outage last this long. The banking regulators would be all over Chase if this was their issue, and they'd probably be facing major regulatory fines and penalties.