actually they have been doing this trend for a long time now, not only influential people but also the rich businessmen like bill gates and elon musk. this resulted in the continuous price upward trend on the price on bitcoin, because the demand for it is very high but lately many whales and rich people sold their bitcoin and now the price is in the downward slope.
I don't think bill gates are involved in bitcoin investment but elon did.
Most people are buying bitcoin or cryptocurrency because they were seeing the price history of bitcoin which is the most biggest investment returns in years, there are no other investment that give so big return compared to bitcoin investment.
More over the decentralized transaction is probably another reason because they could transfer money all around the world.