Outputs like this are able to be "ignored" by a node... That is to say, they don't get stored in the UTXO set.
Normally, you would use this for arbitrary "data storage"... But nothing is being stored here, the "script" is simply "6a" (aka OP_RETURN). So the dust is just being burned. Maybe to reduce the dust clutter in the UTXO set... Or maybe just piss off the wallet owner and destroy all their coins?
I'd say that unless the "real" owner (or at least the person who created these null transactions) comes forward... We'll likely never know.
Does it mean that 8,9 BTC were burned during null transactions? And Bitcoin core doesn't show zero balance, because null transactions don't get stored in the UTXO set?