M2: flushing cache lets page render one time, then blank white page thereafter

I’m working through Alan Storm’s ‘No Frills Magento 2 Layout’ an internal dev server. He walks the reader through small edit, refresh, another small edit, refresh, see what changes, and so on. There are lots of examples. Then I inserted a typo which I couldn’t find, that ended up being whitespace added at the end of 'Magento\Framework\View\Element\Template ' when I copied and paste from the PDF manual.

I then sorted out getting errors enabled, however I managed to get the Magento 2.3.2 install into a bad state where there are white pages on every refresh. Clean the cache and hit F5, the site comes back, but for only one render.

This was a fresh install and I had only executed php bin/magento deploy:mode:set developer as per the install instructions for the module which is part of the book.

I then started an exploration of every command available from the internet in an attempt to be able to hit F5 and just get a page to reload. I issued these two commands:

php bin/magento deploy:mode:set developer php bin/magento cache:disable 

And now the site will refresh with F5 but instead of quickly refreshing, the server grinds for 7 to 10 seconds and then renders Hello World

What mechanism in Magento 2 causes this?
and
What can a person do to get back to how the site was working as expected before all this?

Right now, I believe the solution is to move this M2 and start over by installing a new fresh instance. But that simply is not acceptable; what happens if a live site starts acting like this? Having to clean cache to render one page is not acceptable nor is disabling cache…