How did he get away with it?

>>3278118
Once the Byzantines got control back, they threw him into the river.

>>3278118
God was on his side.

>>3278118
He was pretty much the most powerful man in the empire at the time of his death (Baldwin was an irrelevance and Boniface was clearly a distinct second), especially in Constantinople due to the very strong venetian presence. He was actually offered the throne but refused.
It's not really surprising that he was given a spot amongst the emperors.

>>3278126
Actually tradition says that his tomb was profaned together with those of the other emperors when the turks looted Hagia Sophia in 1453.