It's not clear whether Frontier are running it as a "non-profit" franchise for sentimental reasons or because they genuinely believe that sufficient investment on that basis could return it to a state where it brought in more revenue than it could reasonably spend on itself.
Just a wild stab, and a fairly cynical one at that, but I wouldn't be surprised if FDev have looked at the historical trends of ED (particularly related to the Horizons/Beyond era) and established how long the game can "coast" before it needs new content to maintain interest... and how much effort needs to be put into creating suitable content.
They've probably accepted that ED isn't going to make boatloads of money but if they can keep it rolling along it can generate enough profit to pay the bills and keep the lights on.