The word “crazy” in the title Crazy Rich Asians is an adverb meaning extremely.
I would have guessed that usage began around the 1960s or so, but it turns out that it dates back to the late 19th century.
All of the cites given by the OED seem to relate to a mental state (crazy anxious etc) making me think that perhaps this usage began as specifically as an intensifier of mental states, but a bit of a look around Google Books tells me that there are plenty of early examples of crazy just meaning extremely in other cases.
The Ohio Law Bulletin - Volume 47 - Page 784
Oh, well, but you know Oi was crazy thin.”
The Railroad Telegrapher - Volume 23 - Page 1120
But his engine had been steaming badly all the way from Pinto, and on her schedule, which was crazy fast all night,
My Breeding Herd of Shorthorns in Loose-leaf Form - Page 9
I told him he was crazy high, that I was buying registered cows for $100 each.