He was not the crucial 60th vote for cloture, despite what you may have read on FR. Furthermore, he’s explained his vote many times.
Irrelevant, he voted to end the filibuster. His "explanations" were a lot of nonsensical rambling.
And he'd made a point only a few weeks earlier that the critical votes in the senate are the votes to end a filibuster, not the following vote where only 51 votes are required for passage. He used his critical vote to help pass TPA and by extension TPP.