There are many ways to measure success, perhaps the easiest (though not necessarily the best) is money. Mozilla currently has net assets of >$1billion almost entirely earned off of it's back. It was without a doubt been a wildly successful product for the non-profit and to suggest otherwise is ludicrous. Likewise it continues to earn >$0.5billion/year revenue for that non-profit, to suggest that it doesn't continue to be a wildly successful product is ludicrous.
Could it have done even better for itself? Sure. Being the best possible version of yourself isn't necessary to have been successful though.
Could it have done even better for itself? Sure. Being the best possible version of yourself isn't necessary to have been successful though.