Random tabs opened in Safari and apps opened on IPad that I never opened

It is highly unlikely that your iPad has been "hacked". The security architecture fundamentally inhibits the majority of possible malware vectors. iPadOS does not support remote access to a device unless it has been unlocked by the user - and the user actively participates in enabling access via an appropriate App. In simplistic terms, unless the iPad is unlocked with a Passcode, it has no network connection to the outside world.

The logical explanation is that someone with knowledge of the device Passcode has accessed and used the iPad.

If you are concerned that unauthorised access to your iPad has been obtained, you would be well advised to change your device Passcode. Similarly, as your saved Passwords can be accessed with nothing more than the device Passcode, you might be well advised to change any sensitive account Passwords. If your AppleID Password is stored in your saved Passwords, this should also be changed.