Mageplaza Controller Sample doesn’t display Phtml message

I followed the example from below link but the message “Welcome to MagePlaza.com” doesn’t display.

https://www.mageplaza.com/magento-2-module-development/how-to-create-controllers-magento-2.html

It works up until controller set up , I am able to echo a welcome message from execute function in below controller action file.
app/code/Mageplaza/HelloWorld/Controller/Index/Index.php.

But after I add layout and template my phtml message doesn’t display. Any help is appreciated.