load jquery in footer not working

As Mark Kaplun said in the comments, something is adding defer to your one domain’s script.

If you want your subdomain jQuery script to also have defer, this should do it:

function my_add_defer ($tag, $handle, $src) {
    if ($handle == 'jquery') {
        return str_replace (' src="https://wordpress.stackexchange.com/questions/251298/," defer="defer" src=", $tag);
    }
    return $tag;
}
add_filter ("script_loader_tag"https://wordpress.stackexchange.com/questions/251298/,"my_add_defer', 10, 3);