The water pump failure caused the overheating, not vice versa.
You didn't mention if your engine was a 4 or 6 cyl.
The sixes with plastic impellers seem to have a propensity for early failure. Read the manyposts regarding the same.
Travelling at highway speeds does not require the use of cooling fans; only in traffic.
You were probably using the a/c, which will also greatly lend itself to radiator cooling.
