Have the Olympics/World Cup always been White Elephants or is their devastating effects on the host nation's economy a recent thing?
It depends on two things:
1) The current infrastructure in place to host these events (if more facilities are in place, the less infrastructure is required to be built and prepared for it)
2) The financial ability of the country/city involved to pay for anything required in 1)
It is clearly evident, with regards to the Olympics, that Rio are getting nailed on both points.
It was grossly irresponsible for both the City to bid for the Games, and for the IOC to award the games to Rio. It was like the lessons from Athens were never learnt.