DNS at any company tends to be a mess. Multiply that by a thousand for a large multinational corporation. Case in point, here's Microsoft (and these are never going to stop, due to the sheer complexity):

• https://www.theregister.com/2024/06/28/microsoft_security_certificate_expires/
• https://www.theregister.com/2024/07/08/microsoft_swiftkeys_cert_expires/
• https://www.theregister.com/2023/05/24/microsoft_surface_pro_x_cameras/
• https://www.theregister.com/2022/06/10/microsoft_insider_certificate/

Even when you use an automated service things can go wrong. For example I use Let's Encrypt but it needs to verify my DNS ownership so I use an API token to let the certbot make the modifications to prove that. At some point I wanted to restrict the token rights so it only has access to certain TXT records (to increase security in case the token every gets compromised). Long story short I forgot to include one wildcard and that particular certificate couldn't get renewed so it was out for the day until I fixed it.

Manjaro's website is made for presentation purposes and whether it's up or not has no impact on how the distro runs or whether you can download packages. Furthermore it's a completely different team from the distro developers so this has no bearing on the package quality. I've been a Manjaro user when some of the manjaro.org certificates expired but I never knew about it because it didn't affect me in any way.

manjaro.org uses Let's Encrypt now and it's been recently redesigned.