Sorry for nitpicking, but:
> If nukes were not invented yet, would it really be a good idea to build and sell them as fast as possible (in peace time, no less)?
Arguably, yes.
In this world we've had an inocculation event against use of nukes. Two were dropped, people have seen how abhorrent their use is and collectively decided that they shouldn't be used.
If in the WW2 Japan also had nukes (and delivery systems for them) they'd probably have retaliated in kind and US wouldn't let that slide too and it would have continued for some time.
With the US showing that it will elect mentally disabled people such as Trump, this doesn't seem such a wise decision.
Is the idea to keep the world in balance via MAD? I could see that, though it's a dangerous gamble.
From Richard Rhode's "The Making of the Atomic Bomb", I got the impression that most scientists involved thought they could manage a US or UN monopoly on nukes after the war. General Groves attempted to buy up all of the world's uranium ore. Unfortunately, it is only high grade ore that is rare; many countries have low-grade ore.