Pay-off for the donation of the jumbo jet??

It also might be the quid pro quo for them forcing Hamas into the peace deal.

What's Qatar's benefit to getting a military base in the U.S.? They're a small country with a negligible military, so it doesn't materially affect their ability to project military power anywhere. Which is typically the most direct benefit to having a base in another country.

What it does do, though, is lock the U.S. and Qatar into a fairly tight relationship - and it comes on the heels of Trump giving a nominal security guarantee to the Qataris against any further Israeli attacks, as well as Trump forcing Netanyahu to read off an apology for the previous one.

I would suspect that this is part of the national security realignment that Trump has been pitching to the Middle East in an effort to get his Peace Prize. Dump Hamas, take some oversight role in Gaza...and the U.S. will provide security and will stop trying to force you to change your domestic political structure. Since Trump can't get a treaty through the Senate, creating some irreversible de facto commitments is the best way he can backstop that kind of pledge.