End of the day there is a max limit of flow that any system can take.

Think the amount of water that fell (in 15 minutes ?) was far too much for the system to take hence it flooded.

As for the pitch inspections that took place which resulted in the abandonment of the game none of them took place in the areas that were underwater (corners) or a King Canute attempt of clearance had taken place. They were in the middle of pitch which was deemed unplayable the ref never went and had a close look at the corners which were worse so there was no chance of it going ahead.