Confusing redirect to root domain

I moved this site from the root domain to subdomain.domain.ext as the root domain was going to be switched over to an online restaurant vendor site but we wanted to keep one important page of the WP site still available at subdomain.domain.ext.

I cloned the site and moved it to subdomain.domain.ext and it worked fine. After changing the DNS to point the root domain to a new host the subdomain site is now doing something that I am not sure how to address. If you go to subdomain.domain.ext/wp-admin then everything works fine and I get the login for the back end of the new cloned site (cloned with AIOWPMigration plugin).

But if I go to just subdomain.domain.ext with nothing else after it then it instead sends me to just plain domain.ext.

I have disabled ALL plugins except for Elementor and the special plugin needed for the subdomain page and also set the home page to be the main page of that special plugin. All settings in the General section refer to the subdomain.domain.ext site. Nothing is just domain.ext that I have been able to find.

I see nothing in the htaccess or config file that should be forwarding the home page to the root domain. I also put the WP_HOME and WP_SITEURL variables into the config file to point to the new subdomain.domain.ext location.

Any idea what I am missing here? Or could it be that the DNS info provided for the new root domain host is somehow interfering?

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