Is this correct smart people are cultivating knowledge

Yes, you can.

Is it okay to say brilliant people are cultivating knowledge. Or Brilliant people always cultivate knowledge?

It is not clear what you are trying to ask.

One does not "cultivate" knowledge. That is merely using high-class words to describe something that has no meaning. The same with "smart people".

I should add that people often write or speak that way anyway.

For example Brilliant leaders always cultivate knowledge. Or Brilliant leaders are cultivating knowledge. It's more of an acronym. But I still want to make sure it makes sense.

The ideas are nebulous enough for both to be okay.

Yes, but is it really more of an acronym?

I thought this was a place to get help. Oh well.

We have a comedian in the house.

The only issue I have is that you pair brilliant with cultivating knowledge. If you picture cultivating knowledge as growing or nurturing knowledge, it might make more sense to say scientists or philosophers are cultivating knowledge regardless of it they are brilliant. Maybe teachers cultivate brilliant people. I don't think you have to be brilliant to cultivate knowledge.

Got it

On a different but perhaps unrelated note, such highly educated intelligent people accumulate knowledge.

Also such people may personally be cultivated individuals. Less likely spoken of in English language or described as cultivating knowledge.