Lollipop was the first Android version to support 64-bit processors, but many Lollipop devices (like the original Moto G) were 32-bit. If you download a modern APK that only ships lib/arm64-v8a libraries, it will crash instantly on a 32-bit Lollipop device. You need APKs with armeabi-v7a support.
Here are some top websites for Android 5.0 APK download: Android 5.0 Apk Download
Use this checklist before every manual install on Lollipop: Lollipop was the first Android version to support