The bad news? Steve fucking Jobs still has a devoted postmortem following for no fucking reason except that people felt that cool with ipods and iphones while he was being an abusive asshole to everyone around him and stealing credit from people that actually made things. 
Buddhism probably peaked in %age of the world population around 200BCE-1000CE, when it was spread across most of India and China. Like every religion it’s probably peaking in absolute numbers either now, or sometime in the past half century, at about 500 million.
Super hard to estimate populations far back in time, but seems quite likely more than 1/8th of the world’s population followed it at one time, at least.