They absolutely gave up the shooters information though. They handed over their icloud backups without hesitation which depending on your phone settings, could be your entire phone and everything on it. Your contacts, your messages, installed apps, photos, etc. Most people want their phone to be exactly the same when they restore from a backup, so you have to keep a copy of all of it if you want to restore it.

The FBI wanted access to the phone via a backdoor. Apple had no way of doing it as they didnt know the shooters password. So the FBI sued them to try and force them to add a backdoor to their software so they could try and bypass it. Apple refused because

1. it would eliminate any trust people had with them. Most people wouldnt buy an apple product if the government can just goto them and demand they change their software. Apple and the FBI can say they only added the backdoor once, but with a closed source eco system as tight as IOS, you have no real way to audit or verify anything that happens. the FBI could demand every text message that gets sent is emailed to them and you would have no real way to knowing without a massive amount of work to deconstruct IOS at all levels to verify.

2. 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 (if apple set it up todo that, pretty stupid if they didnt)

There was nothing stopping the FBI, from simply cloning the devices storage, and simply guessing the shooters passcode which if it was a pin, would take a week at the absolute longest but more than likely, it could burn through all the combinations if a matter of minutes.