Rails view is not getting updated

Question

I have a button click that triggers the following function. It calls the below asynchronous request.

    <script>
        function buy_now(user_id, deal_id) {
            var purchase_confirmed = confirm("Are you sure you want to make this purchase?");
            var theUrl = "/orders/create?user_id=" + user_id + "&deal_id=" + deal_id;  
            if(purchase_confirmed){
                var xmlHttp = new XMLHttpRequest();
                xmlHttp.open( "GET", theUrl, true ); // true for asynchronous request
                xmlHttp.send( null );
                return xmlHttp.responseText;
            }
        }
    </script>

orders_controller.rb

class OrdersController < ApplicationController

    def create
        @order = Order.new(user_id: orders_params[:user_id], deal_id: orders_params[:deal_id])

        unless @order.save
            url = "/deals/today_deal?user_id=" + orders_params[:user_id] 
            redirect_to url, status: :unprocessable_entity
        end 
    end

    private
    def orders_params
        params.permit(:user_id, :deal_id)
    end
end

create.html.erb

<h1> Order successful </h1>

routes.rb

ails.application.routes.draw do
  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
  root 'deals#today_deal'

  get '/deals', to: 'deals#index'
  get '/deals/today', to: 'deals#today_deal'
  get '/deals/new', to: 'deals#new'
  get '/deals/:id', to: 'deals#show'
  post '/deals/create', to: 'deals#create'

  get '/orders/create', to: 'orders#create'

  #set all incorrect paths to go to the root path
  match '*path' => redirect('/'), via: :get
end

The problem is that once the create action(shown above) in the orders_controller is called and the subsequent view(shown above) is rendered the screen is not updated with the new view. I understand that I don't understand some concept here. It would great if you could point me to some resources to understand what I am doing wrong here. Thank you for your time.