OP you are in the wrong place if you want to learn the facts about grounding. Try this site, which is run by a physicist who is electrically sensitive and has had to make certain adaptations in his environment: https://www.beneficialenvironments.co.uk/.
The point about grounding mats is that certain items that we use - computers, smart phones etc - give off strong electric, electromagnetic and radiofrequency fields which our bodies are not well adapted to deal with. The body is an electrical system so of course electrical fields will affect it. It's helpful to ground the electrical fields around us, when we are not in touch with the ground with our bare feet, which is usually.
There's a growing body of studies on the effects of exposure to electric, electromagnetic and radiofrequency fields and the effects of grounding. As one example, a study on cellphone radiation by the US National Toxicology Program (https://www.niehs.nih.gov/sites/default/files/NTPcellphonefactsheetjan2024508.pdf) show it induces cancer.
This is just one example. Computers and smartphones and some electrical systems give off strong fields of all the above mentioned types and some of us have to use adaptations to lessen our exposure to the fields, or we get headaches, brain fog, palpitations and other issues. The fields "before" and "after" the adaptation can be measured with an inexpensive meter called the TriField, so you can quickly see if any given intervention actually makes a measurable difference. Note: the TriField and other meters are professional quality tools and don't respond to the placebo effect.
There's more about grounding mats here: https://www.healthline.com/health/under-review-grounding-mats#does-it-matter
Personally I use grounding mats for my computer and the chair I sit in, as well as the seats of our electric car as the electromagnetic fields are very high. They were very inexpensive. I did try a grounding sheet to sleep on but, while these seem to suit some people well, it made my symptoms worse so I will sell it on.
Some companies, where the employees use computers all day, require their workers to wear grounding wristbands, which are connected to the earth via any plug socket. This has been the case for decades so anyone who doesn't "believe" in grounding is far behind the times.
I hope you find the info you are looking for.