Competition is fierce, and luck often plays a big role for breakout apps.

Connecting Wallets and policies..

connecting to the wallet and apple/google’s policy for digital purchases!

Convincing Android users to switch to iPhone.

Notifications

Apple's rules and restrictions, especially for crypto related products.

Not building an app, but I would guess walled gardens of IOS and Android stores.

Behavior change. Getting into the user’s routine.