Yet DDM has failed in three different incarnations and Mage Knight has had issues, while LA is still producing new models.
DDM sold 1,000,000 minatures in the first few months. That's not failure. As an ongoing product, it did really well for the first few years, then the market place became saturated until finally the sales no longer were there... seven years later.
Mage Knight is dead, and has been for years (since 2005). A number of issues killed it, not limited to the woeful game balance of the game the figures were for, and the game's rebooting. HeroClix is still going, but it took a year or two off production as WizKids was folded. Yes, there's a "WizKids" in business now, but I don't know what relation it has to the old. (Name recognition only?)
LA has been going now for four years. It sells an extremely limited range of figures, and to say that Reaper has had problems getting new minis out understates the matter. It hasn't yet had the longevity of either DDM (7 years) or MageKnight (5 years).
This isn't to say that LA isn't a sustainable, successful product line, for it certainly is. It's certainly more sustainable than the DDM line, but it will never approach the profits that DDM pulled in.