One of two things:
You flooded which... well which is really stupid against a Mage or he got RNJesus and SOMEHOW held out until turn 10 and an 8 card combo.
He'd have to:
Nova
CoC
CoC
Blizzard
Blizzard
Nova + Doom Sayer
Flamestrike
Or something along those lines to constantly clear your board every turn to make your scenario make any sense.