He got played by agreeing to the 4 hour delay in the vote. “Oh, OK, let them rant and rave, and then we’ll vote”. They used those 4 hours to figure out a way to turn Flake, and that was the key to making the weak sisters waver as well.
When you are about to win, never, ever give your opponent time or opportunity to take it away. That is how Grassley got played. Most of what he did in the process was OK, and his heart was always in the right place, but he is not tough or good at dealing with those who have no sense or morality. It’s not in his realm of experience.
Personally, I think they had plenty of hours to turn Flake without the 4 hour delay. For me - litmus test was that K got through. I thought Grassley intentionally handed them concession after concession for the public’s view, every concession he conceivably could without losing k - to prove over and over and over (to the public) that every (bipartisan) concession WAS made so that later, when the Dems scream “No Fairsies!” the public will have memory of a slow foot dragging concession laden process. I don’t have a legal background - JMHO