Bezos has liquidated so much AMZN stock he doesn't need AMZN's balance sheet for a piddly $250mm transaction. He might even figure out how to do something he hasn't done at AMZN and that's turn a profit. The last I checked, AMZN still had an infinite PE.
By keeping WaPo remote he can at least create the appearance that AMZN is corporately neutral for whatever news platform ideas AMZN pursues.