So how did a Swedish guy become the most famous Asian in the Western world?
Oland was born Johan Verner Ölund in Västerbotten County, the second most northern and second least populated county in Sweden. His family moved to the United States when he was thirteen. He took to the stage and became a Shakespearean actor and translator of Strindberg. He was vaguely Asian looking, something Oland attributed to Mongolian ancestry thanks to the invasions of Genghis Khan. In Hollywood's hands, he filled the roles of stock villain and stock ethnic character, sometimes both. In The Jazz Singer (1927) he was Cantor Rabinowitz, he was the title character, and incidentally the second most famous Asian character in the Western world, in The Mysterious Dr. Fu Manchu (1929), and he was a werewolf in Werewolf of London (1935). Okay, that last one doesn't count. Lest we think that this is a bizarre anachronism, think about how many ethnicities Scottish actor Sean Connery has played.
Hollywood was such in those days that aside from Anna May Wong and a few others, roles for Asians, even playing Asian characters, were few and far between. White actors playing Asians was the norm. A Swedish guy playing an Asian seems an especially egregious example, and perhaps it is, but there are plenty of strange examples of white guys who don't even vaguely look Asian playing Asian roles. Case in point: John Wayne as Warner Oland's ancestor Genghis Khan in The Conqueror (1956).
So Warner Oland slipped into the role of Chinese detective Charlie Chan with easy. Oland appeared in sixteen Charlie Chan films and the series became a worldwide success. When Oland died of pneumonia in a Stockholm hospital on August 6, 1938, the rest of his final film was reshot Ed Wood style with another actor, none other than Peter Lorre. The Charlie Chan series continued, with much less success, with another white actor, Sidney Toler.
A fascinating look at the Charlie Chan series, Hollywood yellowface, and the inspiration for Chan, real life Hawaiian detective Chang Apana, is Prof. Yunte Huang's 2010 book Charlie Chan: The Untold Story of the Honorable Detective and His Rendezvous with American History.