You're just plain wrong and no amount of sophistry can get you out of the corner you've painted yourself into. You think that capitalists are an undifferentiated mass who share all the same interests, rather than being limited agents whose interests are directly tied to their personal investments, and that those investments are at odds with other interests. Capitalists only collude to repress working class action, but they are in a real way each others' enemies in direct competition for control of a market. Vault-Tec does not have the same interests as Poseidon Energy. Poseidon Energy is the only company with a fiduciary incentive to repress cold fusion. From Vault-Tec's perspective cold fusion would have accelerated vault construction, made the vaults more secure, and commercial cold fusion could have ballooned Vault-Tec's consumer market divisions.
That is why, in real life, it's not Wal-Mart or Target who repress fuel efficient vehicles and EVs, but the automakers and oil companies who profit from excessive consumption in fuel and vehicles. But that's not what happens in the show. What happens in the show is cartoon nonsense that would be stupid to a child.
Clearly Vault-Tec DID think they could get use out of cold fusion or else the Vault-Tec branded core would have never been made. Moldaver's stories don't add up, which is likely intentional but it all comes back to further proving why Vault-Tec is a ridiculous faction with no existential raison d'etre. So the real question remains why does the Enclave have the core but not the code? How did Vault-Tec lose the core to the Enclave?