It's pretty well established that CAPEX is the source of security in PoW not OPEX. See our paper and papers like
httpss://uncommoncore.co/wp-content/uploads/2019/10/A-model-for-Bitcoins-security-and-the-declining-block-subsidy-v1.06.pdf
httpss://uncommoncore.co/wp-content/uploads/2019/10/A-model-for-Bitcoins-security-and-the-declining-block-subsidy-v1.06.pdf
You're literally the first person I've ever heard express such an opinion. Could you give citations for "pretty well established"?
Multiple, please, since it's "well" established. Preferably ones that have citations at the bottom? The document you linked contains no citations and is thus an opinion piece, not an academic paper.