I believe it was because it was such a weird and dramatic shift in tone from the regular CAD content, which was not all that great to begin with. You probably had to be there (I wasn’t).
Hbomberguy did a video on it that explains it well I think: https://youtu.be/TebCHHCw9rY
To add something here: HAProxy’s ACLs are more powerful than anything nginx, Apache or even Envoy can do. Of course HAProxy is not a web server but “just” a reverse proxy that speaks HTTP (and TCP) but what you can do with its ACLs is often extremely impressive in its simplicity and elegance. A single-line ACL in HAProxy would require loading additional modules in nginx and writing a screenful of configuration directives. Though the average self-hoster will probably never need any of the power HAProxy offers.
In the past 20 years I have professionally used all four of these as web servers and/or reverse proxies and I am pretty confident that HAProxy beats all others when it comes to request processing. Though Envoy might be getting there.