It is my opinion that intelligence accounts for a small fraction of what we know.
It all boils down to who can be bothered to do the reading and do their research in the end.
This is why 'smart' students are not naturally like that, they just have a very conscientious attitude towards putting the hours into academic work.
They are 'secret studiers' who claim to not do much work, when actually as soon as they get back to their house the first thing they do is grab a coffee and revise. It's their way of remaining competitive with you; so they brag about doing little work to achieve.
When actually, unless they are gifted, (which they probably aren't) - they are just spluttering lies.
Only <1% of people can naturally take info in and memorise every last word. The other 99% it takes a very long time to get to the same level as the true geniuses.
That's why you need to put 20 hrs a week for 50 years to be considered an 'expert' at something. (Equates to 10,000 hrs).
It takes a very long time indeed to get to knowing lots of things. So people who brag about knowing everything are just being arrogant and silly (unless you've met a bright, smart, gifted genius, which you probably have not).