Passing variables

[eluser]beeLoop[/eluser]
Lets Debug your problem.
In your controller, First check the value of $data['users'].
If you are getting the correct result, then next step.

In views includes/template, it is assumed that you have included the main_content variable.
As in the controller you are passing the value as $data['main_content'] = 'active_users';, so echo the $main_content variable in includes/template view.

That's it for now.
Let me know what value of $data['users'] you are getting in controller.