Installing Windows on an Apple laptop is easy. There's no real reason it couldn't be easy to install Android on an iPhone. Apple has spent a lot of time building software controls to make it impossible, and sues people who try. It's really not asking that much of Apple here - they would save money if they stopped trying to make it artificially difficult to switch from iOS to Android.

They could also pick up customers.

Something isn't easy if it's expensive.

And buy a new phone, figure out why contacts didn’t transfer correctly, take it to a store so they can use a special machine, etc… yeah, super “easy”