Honestly, not surprised. AXP/AMEX marketing team and superior customer service in the early days of the programs made it the top card to own amongst wealthy individuals.
The once coveted "black card" or Centurion product was invite only to existing card holders with the platinum card and met a certain annual spend criteria (some 6 figure amount). Card holders of this product paid some couple thousand dollar "initiation fee" and of course the annual fee. AXP got paid and then double dipped on the merchant side with even higher fees (the "no limit" cards charge a higher transaction fee).
Its exclusivity and hype has died down, especially when it started to issue centurion for businesses. Very easy to hit the required spend limit and use it as a weird flex at your next dinner party or restaurant outing with friends/family.
Honestly, if it wasn't for the centurion product. AXP would just be another credit card company and credit card network out in the wild (maybe it would have just been like "Diner's Club")