More or less the opposite: stock sold off cheaply in the evening got sold for more in the morning. Probably algorithms involved in selling, but more likely they were prepared to take lower returns to not risk holding AIG overnight rather than as some sort of market manipulation strategy

But the main factor in the divergence in that chart in 2008-9 - as one of the comments points out - is that AIG announced a lot of bad news during the financial crisis during the daytime but never collapsed overnight.