The great barrington declaration was not signed by thousands of experts. I am sorry I gave the wrong link earlier to critique by experts of the GBD, here it is.
It is indeed interesting to see who has signed this. There are ten from England, none of them a jobbing clinician who is actually treating patients with Covid-19 or at the coalface. So it really matters very little whether there are a thousand signatories, it matters what they do to have so much more insight.