This is only true in retrospect. When IoT was hot, everyone was eating up that story. A lot of people are still eating up IoT story because of rise in 5G.
Also, competing in server market is very very hard. If they had exclusively focused only on server market for past 5 years, they probably might still have been just minor player because of massive Intel legacy that needs to be overcome but no one knows how.
He made a bad decision in pushing ARM to chase IoT. Instead he could have pushed more in traditional areas - servers, data centers, laptops and desktops. Some of that did happen but more could have been done if they had not been distracted by IoT.
Sure, the valuation went from 33 to 66bn, but could've done a lot better. Just because you made money doesn't mean you didn't do something stupid.