> so hopefully the AI bubble unwinding won't be as bad

It's currently larger than the 1880s railroad boom.

"Overbuilding and speculative debt ultimately culminated in the Panic of 1893, plunging the nation into a severe economic depression."

Not according to Goog's. The railroad bubble of the 1880s was supposedly 60+% of the market. It may not be accurate though.

"During the 1880s, private railroad enterprises represented over 60% of the total capitalization of the entire U.S. stock market, peaking at 63% in 1881 and 1885."