Why does the Internet stop working after upgrade to iOS 8

So I upgraded my friends 1st generation iPad from iOS 4 to iOS 8.1 on my MacBook Pro. Now he's complaining that the Internet sometimes doesn't work and when it does it works extremely poorly and he's blaming me that it's due to the iOS 8 upgrade. Was the iOS 4 version 1st generation iPad not supposed to have been upgraded to iOS 8.1?