This kept happening to my friend. Finally tracked down at least part of the problem. She has a couple of iPads that are linked and synced with her iPhone. These iPads are used by her grandsons when they visit. The iPads have/had minimal security enabled. The grandsons would install various games which would then appear on the other devices. Voila!

A 7 yo and a 10 yo are extremely adept at navigating the various safeguards supposedly in place. I have over 50 years in the industry and I am overmatched When I visit her next, I will continue trying to secure her systems, but as long as they have physical access, its a losing proposition.

It just bugs me that these app makers will "assume" that I want their shit.

I don't have personal experience in that environment, but did a quick search and found this:

"Motorola phone keeps installing unwanted apps

"Go to settings and the apps section. Show System Apps and Search for an App called Mobile Services. Disable that. Problem solved."