Why does HTTPS show the website of a different domain?
When visiting a domain using https, Apache will serve the top matching Virtual Host with the matching IP address. If there is no existing Virtual Host for the requested domain, the Apache service will instead return the first one for that IP address. An HTTPS Virtual Host is not created for a domain until it has an SSL certificate installed.
The first time you install an SSL on the Shared Virtual Host IP for the server, that domain will be the default SSL. After multiple certificates have been installed, the setting to select which one you want as the default will appear in the WHM interface Manage SSL Hosts. The default SSL feature is designed to allow control over how the Apache web service handles these requests.