The researchers first became suspicious when they could not replicate many findings:
The Purdue researchers originally began questioning the dataset when they could not obtain similar outcomes from their own tests. That’s when they started analyzing the previous results and determined that a lack of randomization contaminated the dataset. – Purdue University, “Researchers Uncover Blind Spots At the Intersection of Ai and Neuroscience” At Sciencedaily (December 15, 2020)
News, “New findings debunk many studies claiming to read minds via EEG” at Mind Matters News
So many “eye popping” findings were based on a simple error of failing to randomize the data.
You may also enjoy: How far has AI mindreading come? Further than we may think. And some trends are troubling. On the one hand, high tech can help the blind see and amputees feel. It’s not a miracle; the human nervous system can work with electronic information. That said, one AI ethics analyst notes, we are heading complacently into a world of brain transparency with no protections in place. (But maybe a lot of it isn’t true anyway,)