Because you know everything that's involved in the deal, and why both Governments were very keen to do something about it?
Ultimately we know virtually nothing about how likely it was the we'd lose access to the islands, what the benefit of keeping the lease is, what security issues are involved, what arrangement we have with the US etc., etc.
If you're someone senior in the MoD, on the Privy Council, a Cabinet minister, or a senior FCDO official, then I'll accept you have enough knowledge of what the actual deal is, and what the stakes involved are.
If you're not, then you know as much as I do - and that's not enough to actual know whether it's a stitch up or a great deal.