Mead was never a common drink, nowhere near as widespread as wine or beer. If it is to survive in Western Europe (it did in Poland, Russia and the Baltic), it will have to be as a status drink, something to mark certain occasions or to demonstrate refinement. IOTL it lost that position and by the 17th century had effectively become medicinal.
Quantity is not a big issue. The constraints of beekeeping mean that it will never be as readily available as beer or wine, but it needn't be. Champagne is in very limited supply, but that hasn't hurt its status or symbolism. And for all its relative rarity, honey was available enough in medieval Europe to make a trade good. The Hansa even exported it. If people had wanted to make mead, they could have made enough for every high-status family to drink it occasionally.
Unfortunately, I don't think it's as simple as to stop the Norman Conquest. Scandinavia and Northern Germany had long-standing, unconquered Germanic cultures, and they stopped drinking mead in large quantities, too. What might be required is stopping the dominance of French courtly culture and Salernitan medicine. Neither system had any space for mead or beer, so the high-status drink of choice became wine. Beer can survive that by dint of being the only option for everyday consumption in much of Europe. Mead is much more threatened, because people can easily choose not to drink it.
Or maybe the Romans can adopt mead as a specific ceremonial drink in late antiquity? Hard to see why, but the cultural cachet could establish it at the Carolingian court, and it'd be plain sailing from there.