Until recently, few people had heard of Bryan Johnson, a tech entrepreneur from Provo, Utah, though the odds are high he had helped them spend their money without them knowing it. Johnson made a fortune after his e-payment company Braintree bought Venmo in 2012 for about $26 million and then sold it a year later to eBay for about $800 million, fulfilling a goal he set for himself at age 21 and making him rich enough for several lifetimes.
“Following the acquisition, a single question…

