Effort without intelligence is just pointless toil though. Either this paper is saying it’s pure chance, in which case effort isn’t relevant, or some intelligence is required.
Fundamental reality of intelligence is that it can be shared. Especially more effective when it is only shared among small groups. Very few are innate to a person.
If you're saying "intelligence" as in greater than 75 IQ then sure.
If you slide that scale any further you'll quickly be overweighting intelligence to success
Show me all of the company CEOs with an IQ of 80.
Well, considering that with "zero intelligence" you're basically on life support in a coma, I'd say you're not even wrong.
Lot of folks who become rich with average intelligence so it's in no way a barrier.