Car play audio auto start

When connected to Car Play, accessing any app on my phone that has the capability of playing sound, causes the app to override my stereo sound. For example, phone is connected to Car play (in this instance using Blue Tooth) to FM/Sirius/whatever, I open my phone to say the Weather Channel app, this immediately stops my car stereo presumably because the Weather Channel app has the capability of producing sounds. Make it stop! Is it because I’m connecting via Blue Tooth? It does this even on game apps that I have the sound turned off in settings. Totally annoying when my husband is driving and we want to listen to music while I troll my phone.