Welcome to Android Central! There are a few possible reasons for an app like that auto-installing:
1. It's bloatware that came with the phone, put there either by LG or your carrier.
2. It's bloatware that was added to the phone as part of a recent system update -- this is unlikely, since the Stylo 3 is an old phone and probably hasn't gotten an official update in several years.
3. Some app you installed is causing other apps to auto-install. I don't think this is allowed on the Play Store (although there are probably some apps that slip through), but it's more likely if you install apps from other sources.
4. You unwittingly agreed to install the app as part of a browser popup ad, or perhaps an ad break in a game that you were playing.
Are you able to uninstall the app? If so, does it reinstall by itself?