You have to trust play store.
Why having to trust play store?
Isn't much better to download the apk file directly from the official website? Or at least going to play store by clicking on the link provided on the official website?
These should be much better than going to play store and searching for electrum.
That's right. There are many phishing wallets pretending to be official apps, so it's always a good idea to check if the official wallet website offers the APK file. Users should allow installations outside the Google Play Store in their settings, which is blocked by default on Android. They should then disable it or be very cautious when installing any apps outside the Play Store (checking the sources, URLs, pgp signatures, etc.).
On the other hand, this isn't possible on iOS devices, since Apple's system only allows installations of apps from App Store.