How could you know the Senate was going to fail it? You'd heard four senators express opinions, two of them extremely favourably. The conclusion you made from that I would without a doubt term "cold feet."

If things actually did start to look like they were going south, than I'd be in favour of pushing to table or withdraw it and address their concerns in the mean time, but since we didn't wait that long, the concerns weren't very well spelled out. There was zero advantage to withdrawing it at that time, and in fact severe disadvantages.