App not starting any Activities on launch

So I already figured out a solution to this but wanted to post it in case anyone else came across this problem, and maybe someone can give me further insights into why this happened…

So I followed the book in chapter 8 all the way up to right before Binding List Items

Once I reached that point I tried to run the app and kept getting a blank white screen.
First thing I did was set breakpoints in basically every class to see where execution was going.
I wasn’t getting any errors or crash reports in logcat

When running in debug none of the breakpoints were being hit and still was getting a blank white screen.

From there I looked around and made sure all the code was correct, it was. But still no change.

SO… I restarted the project but this time instead of creating a class and subclassing AppCompatActivity, or in this case SingleFragmentActivity, I used the built in Activity creation tool. Except for on SingleFragmentActivity since its only used as an abstract and never run itself…

By doing this everything worked and I was able to run no problem.

Is there some process that Android Studio does in the background that is missed by the book or possibly just missed by me? I did make sure that on the first attempt the manifest was correct ( checked it many times lol ).