How to forward all requests starting with a specific folder name to the same folder

To achieve this you don’t need the .htaccess in the servers directory itself. You can remove this and apache can use rules in the root WordPress .htaccess to do the rewrite you need, and you can usefully keep rewrite rules for your site in one place.

You need a couple of rules to make this work:

RewriteRule ^servers/index.php - [L]
RewriteRule ^servers/(.*) servers/index.php?page=$1 [L]

These say:

1. If we’re already requesting a page that starts with servers/index.php then quit process rewrite rules. This is there to stop redirect loop errors
2. Any pages that start with servers/, redirect to servers/index.php, passing everything that was originally after servers/ to a parameter in index.php if you need it. E.g. this will send servers/foo/bar to servers/index.php?page=foo/bar

Edit: You need to place these rules before any other RewriteRules or RewriteCond statements so that they get processed first.