Any idea about why it was deleted? (or for the CloudFlare employees/managers/CEOs who hang around HN: Why did you delete this?)

Once the information is out there, it's out there, as the Internet Archive proves. So it can't be about hiding security details (they should also know security by obscurity is nothing to brag about).

Are they no longer happily using Vault? Then update the blog post instead of trying to hide that they were ever using it, then you'll actually help people instead of just confusing them.

All in all, this whole thing is looking very fishy.

Hashicorp still has a tweet linking to it https://nitter.eu/HashiCorp/status/1521973445248040960#m