why do these rich people see bitcoin as a threat?
Rich people dont see bitcoin as a threat. Some people think like that and is an incorrect question.
they can't stop people knowing about cryptocurrencies! with so much money, they can totally learn about bitcoin and altcoins and then invest in that now is a perfect time for crypto investment. I'm just confused

Yes you are. Because you assumed something that is wrong or possibly wrong. Some people are pro-crypto and some are anti-crypto. These people may be rich or poor, but both rich and poor are part of both the groups.
Just assume that many rich people have invested in crypto while many have not. Point remains the same - bitcoin is people's currency, it does not change going into hands of rich or poor. But logically speaking the rich people have a higher capital at hand and are more likely to buy crypto more than what a poor person can afford. Therefore the rich will accumulate more bitcoins and become even more rich while the poor will remain poor.
