Well, because
https://rowlandearthing.co.uk mentions a research paper (without giving the full bibliographic reference, see
https://rowlandearthing.co.uk/pages/science), I ferreted it out
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3265077/
And right at the end it says:
G. Chevalier, S. T. Sinatra, and J. L. Oschman are independent contractors for Earthx L. Inc., the company sponsoring earthing research, and own a small percentage of shares in the company.
So it was not an independent paper at all.
The page of papers cited on the next page relate to elite athletes, those with hypertension, and are often written by those with a vested interest.
So actually complete bunkum.
Craig