Why do corporate research publish papers and attend and present at scientific conferences on AI and quantum computing regularly? Why does it seem like with every innovation of one company, the other companies and startups are just one step behind?

Who exactly do you think develops AI at these companies? Business school grads? MBAs? Young coding boot-camp go-getters looking to strike gold with a killer app?

Get your head out of the conspiracy sand and read an actual piece of information by a professional on what the industry actually looks like (and, as they hire high-demand highly specialized scientists, what they get in their contracts). Then come back if you have a serious question of whether a groundbreaking discovery will be kept a secret.

[Edit: on third reading of OP's post, it's more clear what they are arguing. Thus my post here is now a message not to criticize OP (which wouldn't make sense given their post), but rather is more or less my supplementary argument of the same essential point as OP -- which is that nobody is hiding an AGI (though I don't know if OP agrees with me that at this stage no corporate R&D will hide an AGI).]