I kept waiting to see water dumped...or the entire line and bucket jettisoned......both of which are simple to do.
As it was not done....then you have ask why it was not done.
If your bucket is adjusted to limit the amount of water you take in.....a manually done procedure...then going over weight would have only occurred if the Dip Site parameters changed or the max weight calculations were done for less than full fuel and more fuel was aboard.
If using the US Forest Service Load Calculation system....over weight would not be a factor due to how conservative their performance calculations are determined.
Gordy can explain how that works, if he will, as he does lots of US Forest Service work with multiple types of aircraft.