Rails aways renders the application.html.erb instead of wanted views

My Ruby on Rails application always renders the layouts/application.html.erb view instead the views I want it to. Has anyone an Idea why that might be so? My routes file looks like this:

   Rails.application.routes.draw do
     root 'startup#index'
     resources :users
   end

And my application_cotroller.rb is pretty much empty:

   class ApplicationController < ActionController::Base
      protect_from_forgery with: :exception
   end