This, compounded with LS's spectrum portfolio, which if I recall correctly was around 35 MHz FD in ~1500 MHz. So you can do LTE with PCS voice/EvDO spacing and everything just works. Well, except for the whole GPS deal.
As for why Sprint didn't do NV with Clearwire in mind, they were trying to work with LS, and Clearwire was yet another moving piece in the puzzle. Now that LS is off the table, they can concentrate on CLWR. The flip side of this is that, for a mobility-focused network, you don't want, nor do you need, Clearwire TD-LTE on every site. In a metropolitan area you want to go after clusters of close-together sites where heavy capacity is needed. Suburban/rural sites? Heck, they may or may not get SMR LTE, let alone 2500, due to the added expense of putting panels/line cards up.
The situation changes when you have a sugar daddy (SB) that wants economies of scale on TD-LTE 2500 equipment. Your marginal cost per site goes down, and your political incentives to roll out the network go up. So you put TD-LTE 2500 on more sites than you otherwise would have, partially by making sure that Clearwire will adopt whatever deployment strategy you want them to have. As an added benefit, you don't have capacity problems...pretty much ever...on the sites where you've got PCS+2500+SMR LTE, since you can stack TD carriers to your heart's content and go to 60-degree sectors without too much of an issue (2.4GHz panels are quite reasonably sized, and, I imagine, so are 2.5).