Surprisingly this Bitcointalk ranks quite well even without SEO, but that's one hell rare of a case without any reliance on such.
You can thank the ancient 2009 domain and the thousands of backlinks from other sites for that
Does it rank well? Really? By what big search query in Blockchain, Crypto, Bitcoin niches it ranks well? "cryptocurrency", "what is bitcoin", "buy bitcoin", "what is crypto", "how does crypto mining work", "what is blockchain", etc. the forum isn't close to the top 10. Almost half of the traffic is direct visits (I assume) and it ranks only by brand names or keywords with "forum" in it.
The bitcoin keywords are HEAVILY competitive and there's swathes of web pages optimizing for all those above keywords which is why you don't see BTCT anywhere close to there.
Fun fact: all the bitcoin keywords have a volume of like <5000, except for "bitcoin price" which has a whooping 250,000 volume which shows just how many more people search for that than anything else (including investors, nocoiners, journalists and such). I'd show you a pic of the LSIgraph of the keywords but they want me to pay $1,000 a year for the access.
SEO is, as I found out, one hell of an expensive job.
Still, searching for terms in the page should yield that page, even if the last in results, not ... just vanish.
I find the last changes of Google a total #fail. Actually since yesterday I also switched to DDG, although Google served me wonderfully since its early beginning.
If that annoys you then wait until you hear that neilpatel.com site (a well-known SEO agency) told me that Google makes around 8 algorithm changes a
day!