Source : The Verge
These people have access to excess money. These money comes from us who buys China made iPhones at US made pricing. So it's no wonder that Apple is a trillion dollar company and a CEO of the company, Tim gets a handsome bonus which basically sits in his account making zero inflation adjusted profit. So people with such deep-pocket are exploring options to invest their money elsewhere and considering the performance of crypto, there's no better choice right at this moment.
So what Tim Cook did, is just a wise step to make use of his unused money in the best possible way! While it's not a news which will impact bitcoin super positively, but possibly win some trust of common mass. Nothing major!