Why do you think a $10B contract is inherently controversial? The US spends 100s of billions on defense procurement every year, and even 100s of billions on individual programs (spread out over multiple years). The F35 may end up costing over $1T when everything is said and done. But a program that costs $10B over 10 years is what signals the rise of the military industrial complex that Eisenhower warned about?
And why does Biden owe Amazon/Bezos?
Certainly not the rise of the Military industrial complex, or a even a peak , but perhaps a regular routine part of the complex that should not go uncommented on. That they addressed Amazon's complaint that the contract was unfairly awarded by creating a new contract with only two vendors allowed to even tender bids is probably the most concerning part to me.
And why does Biden owe Amazon/Bezos?
Amazon Web Services played a very key role in the unified tech censorship of Biden's presidential rival and his continued suppression. The destruction of Parler by AWS was the worst part of the whole episode. I believe this was a very bad act with extremely negative consequences for the free flow of thought and information in our society. A former President and billionaire can still be heard but hundreds of millions have had their voices threatened and many rightly fear that with a "wrong" comment they can be "erased" from the internet without any recourse.
If someone argued that Biden didn't owe Amazon but feared them based on the example made of the previous occupant of his office I would be sympathetic to that line of argument.