McGovern was an attack dog type, and Gans I think had some issues with pressure fighters. McGovern lands some good one before the 1st knockdown. If you have a good quality film, you can see Gans' knees wobble just before he goes down backward. Gans was a skilled puncher in his time, but not the most durable type. He lost twice via KO before meeting McGovern. When a skilled swarmer with a lot of power ( McGovern ) meets a skilled boxer type ( Gans ) , the boxer type is going to need to get his respect. Otherwise, he's in trouble. Gans can't set his feet and fire back due to the pressure, but he does land himself a few times. Gans lost to other attack oriented fighters later in Sam Langford and Battling Nelson. So there is a trend of forward moving durable types beating him. A key takeaway. IMO, McGovern blitzed him, had Gans' equilibrium off by landing punches, including the one he landed behind the head on the first knockdown. Gans could not deal with McGovern by out muscling him in a clinch or by getting his respect with punches. If it was a fix, Gans could have stayed down instead of getting up six times. The story of the fix comes partly from the referee George Siler. Siler, who was fond of Gans aids him in the fight by escorting Gans to his corner after a beating in round one. Since when do ref's do this? People lost money betting on Gans, so they scream fix. This isn't the first time I've seen Siler do something questionable on film. He allowed a buzzed Fitzsimmons a few extra seconds when Corbett was getting to him, didn't he? Yes, and you guessed it, Siler was a fan of Fitzsimmons. The result seems genuine to me, and we have the film to judge.
There was also another statement in February 1906. https://chroniclingamerica.loc.gov/lccn/sn83045366/1906-02-21/ed-1/seq-8/
In the end, so many people viewed it as a fake, and the betting was so weird, you pretty much have to concur with that assessment. That said, I have seen more suspicious KO's.