If anyone cares, I found a post over on his sub has a theory that explains it:

The first time you visit DEIdetected.com you will see a screen showing : "Vercel Security Checkpoint" (try this in incognito mode)
Vercel is a web cloud platform for hosting websites. one of their feature is DDoS protection which can be enabled at will.
However, levaving this protection on will prevent google robots to index the website. (Source: https://vercel.com/docs/security/attack-challenge-mode#search-indexing )
Indexing by web crawlers like the Google crawler can be affected by Attack Challenge Mode if it's kept on for more than 48 hours.
The ownwer of the website enabled the DDoS protection on but forgot to turn it off. you usually turn it on when your website is being DDoSed

Human error and conclusion jumping. Can personally confirm it works fine now.