why can't I bypass Activation Lock to restore my iPad?

You can only get past Activation Lock with the Apple ID and Password of the original owner who set up the iPad. If you are the original owner Apple will help if you can provide the original receipt clearly showing the serial number. Check this link...

How to remove Activation Lock - Apple Support

I'm sorry we cannot help and Apple will not without the receipt. Activation Lock is a theft prevention feature which cannot be bypassed. An 8 year old iPad is an antique which cannot run today's software. You can recycle it at any Apple Store.