Only because they knew it had the votes anyway....I suspect if they needed more Republican votes to pass it, some of them would have gone along.
So....what should we do?
Vote for the Dems?
Stay at home?
Throw votes away on third party candidates (effectively the same as voting Dem)?
Here in CA I have always voted the straight GOP ticket without exception and never regretted it. Sure we have the usual contests of moderates and conservatives competing in the primaries. But the Dems in my state, without exception, are ALL Marxists.
The choice is easy.