That sweet million dollar purse means that the match has to sell enough tickets or pay-per-view to cover that purse, and for everybody involved to make money. Early in the 20th century, legitimate wrestling put bums on seats. George Hackenschmidt vs Frank Gotch for the World Championship in 1908 filled a venue that seated 10,000. Their 1911 rematch took place in a larger venue, and filled it to its 35,000 capacity.

At this time, professional wrestling was generally legitimate. There had been fixed matches, including back in the 19th century. The same was true of boxing, and many other sports. The transition to fakery was due to marketing. In particular, after Gotch retired due to poor health (and died young a few years later, due to kidney disease (possibly due to syphilis)), Ed "Strangler" Lewis was the dominant wrestler in the US in the 1920s, becoming the World Heavyweight Champion after defeating Joe Stecher in 1920.

The problem: Wrestling was not interesting enough for the public, and its popularity was dropping. Matches averaged about an hour, and most of the action took place on the mat, a slow and barely-visible struggle of position and endurance.

Lewis, his manager/trainer and wrestling promoter (and wrestler) Billy Sandow (AKA Wilhelm Baumann), and fellow wrestler Joseph "Toots" Mondt came up with an answer: make wrestling spectacular. Make the action more visible, develop fancy new holds to excite the audience (Mondt helped invent many), and have some back-story, rivalries between wrestlers etc., to further excite the audience. Mondt's more visually-appealing style, "Slam Bang Western-Style Wrestling", the ancestor of modern professional wrestling style, was a hit with audiences. Mondt also added time limits.

Why didn't wrestlers wrestle in Mondt's appealing "Slam Bang" style before? Simply because it wasn't a good way to win wrestling matches. Spectacular moves were an invitation to be taken to the mats in an inferior position, and slowly defeated in the barely-visible on-the-mat wrestling. With "worked" (i.e., pre-determined) matches, this was not a problem. There was no risk in using spectacular moves, because the outcome was pre-planned. Mondt went beyond just pre-determined outcomes, and choreographed sections of matches, especially the endings. Audiences loved it, and Lewis, Sandow, and Mondt were hugely successful, earning the nickname of the "gold dust trio".

The new style of wrestling attracted audiences due to its visual appeal, and also allowed controlled shifting of championship titles from wrestler to wrestler, to have more frequent championship matches, and to build rivalries. This worked, despite occasional problems. In 1925, Wayne Munn, selected by the Trio as their next champion, became the first truly fake champion. Without even close to the skills needed to defeat Lewis, he won the championship, greatly surprising the audience and most betters (and presumably greatly enriching the Trio, who knew which way to bet). A few months later, he fought Stanislaus Zbyszko (former champion due to a worked victory against Lewis), to build his credentials as a great wrestler. Zbyszko had other plans, and refused to follow the script, winning the championship with great ease. Joe Stecher, also a former champion, had split with the Trio, and with his brother Tony was attempted to build a competing promotion - they had bribed Zbyszko, who then wrestled Stecher the following month, and Stecher, and his promotion, controlled the championship. Stecher was champion for 3 years, until Lewis beat both Munn and Stecher to become undisputed champion again in 1928. Zbyszko's double-cross of the Trio kept championships in the hands of credible wrestlers for a long time to come, to avoid another embarrassment like Munn's pushover defeat.

The Trio fell apart later in 1928, when Mondt fell out with Sandow's brother, Max Baumann, who was after a bigger piece of the action. However, fakery as the way to earn money through wrestling was well-established, and professional wrestling remained fake.

Wrestlers wanting a professional career followed the money. The advent of television didn't change the importance of visual appeal to the audience, and fake wrestling remained the money-maker.

The Ultimate Fighting Championship (UFC) faced a similar problem with the audience-boringness of wrestling in their early years. Their first event, UFC 1, with only 1 of the 8 fighters adept at ground-fighting (Royce Gracie; the only other wrestler was a Sumo wrestler), had short fights - of the 8 fights, half were under 1 minute, and the longest under 4.5 minutes. UFC 2 featured 3 wrestlers, but only one bout (taking 1:31) was wrestler-vs-wrestler. Matches became longer with UFC 3, with 3 exceeding 4 minutes (Royce Gracie withdrawing from the tournament due to exhaustion after his 4:40 victory in the first round). Still, there were no long wrestler-vs-wrestler matches, until UFC 4, when Royce Gracie met Dan Severn, former amateur wrestler and WWF professional wrestler, in the finals, in a match which went to ground and stayed there, in the old "boring" style of mat-wrestling for 15 minutes until Severn tapped out. The final of UFC 5 was a drawn fight of 36:06. This was not the way to win audiences, even if television made the on-the-mat action more visible than in the early 20th century. Following a similar 33 minute draw in the final of UFC 7, the UFC introduced time limits (15 minutes for semi-finals, 30 minutes for finals) and judges - if neither fighter could force the other to submit in that 30 minutes, at least the judges could declare a winner and avoid a drawn tournament. Later events introduced rounds which brought shorter time limits, and brought fighters to their feet again. Without these steps to keep fights interesting to the general audience, it's possible that the UFC would not have survived, even with their ability to reach a much larger audience through cable TV than had been available to wrestling a century earlier.

In summary, professional wrestling needed money coming in to maintain the "professional" part (i.e., to pay the wrestlers). "Real" wrestling lost its audience, and "fake" wrestling took over because the audience liked it better,.