Advertisers became some of the richest men on the planet, somehow convincing people that tracking every single mouse movement on every webpage made advertising unimaginably valuable.
Ad-men have been some of the richest men on the planet long before the word 'mouse' referred to something other than a small furry critter.
Really? Honest question. The 19th century Robber Barons were bankers and industrialists -- Morgans, Carnegies, Stanfords, and Rockefellers. Before that it was slave-owners and more bankers and industrialists -- Rothschilds and what-have-you. Back in the Middle Ages it was extortionist thugs, a.k.a. the nobility -- Louis the nth, Henry the kth, etc. I guess the clergy were always fairly well-to-do, but most people wouldn't consider them ad-men.
EDIT: I see where you may be coming from. Newspaper barons like William Randolph Hearst? Sort of, but his papers offered both "creative" and "editorial."
Please look up agency salaries before making that sort of statement. There's decent executive comp at the top, but there's a reason for the industry stereotype of being underpaid and overworked. It is also why so many from the agency side flee to the brand side.
Ad-men have been some of the richest men on the planet long before the word 'mouse' referred to something other than a small furry critter.