I have also try install garmin apk on different Android car stereos with Android 7/8 and the same result.. logo starts then black screen.
In all the cases i was copying garmin folder to the main root internal memory.
But with cell phones (ej: like a lg g6 or moto z2 play with Android 8 no rooted) i was able to succesfully run the apk with no problems at all...
I believe car stereos had some sepcific issue with garmin apk (no matter what folder structure you are using)