Google Maps and Apple Car Play

When I unplug the USB cable connecting my iphone X from my 2017 Honda Pilot while running Google Maps on Apple Car Play, it stops my Google Maps navigation on my iPhone. This also happens when I turn my car off. So, for instance, I'm going on a long road trip and stop to get gas - I turn my car off and my Google Maps directions stop running on my phone. When I turn my car back on, I have to re-enter my destination and Start the Google maps navigation again. This also happens if I disconnect the USB cable while driving - it stops the app from running on my phone. I understand why it stops navigation on my car (it's no longer connected to it) but I don't understand why it turns off the navigation on my phone. Is there any way to stop this from happening?