What exactly is the tax benefit to giving away almost all of your wealth? Tax loopholes reduce your taxable income, which lowers your tax liability. I don't see how you can come out ahead giving away almost everything. Can you explain what you think he is exploiting and what the benefit could be?
Bill Gates has already won at Money, why do you think he'd still be interested in playing?
What impresses me most about his epic win is that he's still #1 in the world for net worth (or occasionally #2 or #3) -- can you imagine if he was still actively trying to get even more personally wealthy?