Loop inside page template not working

From https://wordpress.org/support/article/creating-a-static-front-page/,

Posts Page: (if not already created) create an empty page. Give it a Title that will be used on top of your posts list. This step is mandatory as you are modifying the WordPress default setting. Any other content other than Title will no be displayed at all on this specific page.

So, When you set it as Posts page, Your loop is ignored.

You can set it as static front page (Homepage) or a normal page with custom page template.