Yes, the Khmer Rouge government fell because of Pol Pot's absence and escape, because he was a dictator who imposed communist-style farming on the people. In ruling with such an iron hand, the people were scared to fight for freedom. Literally millions of people died during his reign. The Khmer Rouge government fell shortly after he fled to the jungles.
The Khmer Rouge government fall because of Pol Pot's absence and escape for sure. Without this leadership, which was consistent beforehand, the government was bound to fail, and it did. Any abrupt change in leadership always brings negative consequences to a system. There is no way to change history, but it would have been a different world had he stayed in power.
Pol Pot was a ruthless leader so I would have to say the Khmer Rouge falling was partially due to his absence and escape. Apparently there was no one in his ranking that were quite as ruthless and as cunning as he was. Overall, things may have been very different if he would have stayed.
The fall of the Khmer Rouge regime in Cambodia fell as a result of the government doing unspeakable acts of horror and genocide against its own people in the name of creating a Utopian, farming, communist state. Pol Pot was the guiltiest of the government officials, and the Khmer Rouge certainly did not fall beacuse he fled.
I do not think that the escape of Pol Pot's was the reason that the Khmer Rouge government fell. I think while the absence and escape of Pol Pot did contribute the failure of the Khmer Rouge government, there were also a lot of other problems and factors that caused its fall.