I would be suspicious of a reasonably popular blog claiming to have predicted stuff and not being able to back that up with an archive.org capture (or raw scraper data), though I guess it is somewhere where storing a hash on a blockchain may offer some benefits for edge cases.
If I were to write a dozen blog posts today, and then straight up dump them on my blog, dating each of them so they're spaced roughly evenly since Jan 2021 to today, and start each of them with a preamble saying "I wrote this in my journal around [backdated timestmap]; publishing it now ([real timestamp]) as part of my 2025 blog revival commitment" - what would you say then? This little preamble explains both the sudden appearance and lack of any prior traces on the Internet corresponding to claimed creation dates. Are you going to call me a liar?
No, if someone with even half a brain wants to fake expertise this way, you won't be able to tell. If anything, what will give them away is anachronisms in text. Like idk. an off-hand remark about ChatGPT in a post dated 2021 could make you wonder.
I tried to write out an initial spec here, but I haven’t been able to write any implementations yet: https://github.com/sebmellen/proof-of-origination.