.htaccess rewrite does not trigger on main URL - .htaccess

Question

I have two different domains who I want to point to separate folders on my server.
This .htaccess file is what I have currently
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^(www\.)?foo\.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /foo/index.html [R,L]
RewriteCond %{HTTP_HOST} ^(www\.)?bar\.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /bar/index.html [R,L]
(Note that the [R] option is only there so I can see what is (not) happening while testing)
It works fine if one goes to www.foo.com/asdf or www.bar.com/something
However, simply going to www.foo.com or www.bar.com (with or without the www. subdomain) won't trigger these rules for some reason.
What am I doing wrong?

Answer 1

It is happening due to RewriteCond %{REQUEST_FILENAME} !-f failing for your home page (index.php or index.html) since either of those files will be found. You set your rules like this:
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^(www\.)?foo\.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ /foo/index.html [L]
RewriteCond %{HTTP_HOST} ^(www\.)?foo\.com [NC]
RewriteRule ^index\. /foo/index.html [L]
RewriteCond %{HTTP_HOST} ^(www\.)?bar\.com [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ /bar/index.html [L]
RewriteCond %{HTTP_HOST} ^(www\.)?bar\.com [NC]
RewriteRule ^index\. /bar/index.html [L]