>They handed over their icloud backups without hesitation

Of course they did, the FBI had a warrant. They follow the law. It is the user’s choice whether to use a cloud backup, however. You can use encrypted local backups if you prefer.

>because even if they did create a backdoor to let them bypass the password, most of the data would still be encrypted with the devices password

The back door the fbi wanted was a way to inject and run cracking software on the device. Most people’s passcodes are 4-6 digits. That’s trivial to crack, except that the OS (and in more recent phones, the Secure Enclave hardware) limits the rate of decryption attempts. IIRC the FBI found an Israeli company that used security flaws to do exactly that.

>There was nothing stopping the FBI, from simply cloning the devices storage, and simply guessing the shooters passcode which if it was a pin

The pin is entangled with a hardware encryption key physically built into the cpu. Cracking the encryption off the device is practically impossible.