you didn't do anything wrong: openvpn needs a directed (i.e. non-VPN-ed) route to the VPN server itself; if you want to view a website hosted on the VPN server itself then browse to the VPN IP of the server, e.g.
https://10.8.0.1
if you want https://<site> to always go via the VPN tunnel then you'll need to pull some DNS tricks