Judges confirmed on Reddit that, if they wanted to, it would be extremely easy to mark someone's cards intentionally. While two judges check the deck, only one actually goes and picks it up and there are many opportunities to step aside and do the deed. Now a judge obviously wouldn't do that for no reason, but this is a high-level competition with a lot of money on the line. It's possible another team bribed a judge to mark the cards.
I'm not saying I believe he's innocent, to be clear. I've got no idea. We probably will never have any idea. But it isn't completely outrageous.
That would be a worse scenario than Yuuya actually cheating. More drama than an episode of Drag Race.