FDE is not the only thing they sell.
Software Licenses for their products (Gotham/Foundry/AIP) is why countries (and businesses) deal with them.
That's literally it.
It's not even particularly good technology.
They have a lot of "forward deployed engineer" roles which basically means staff with security clearances who get locked in SCIFs and provide on-site technical support.
Which is really why they keep getting hired: when you write into your contract "it stays on premises and technical support can't take logs off site" they agree to it (at a hefty mark up because all of that sucks to do).