You understand that the people playing Turtle don't pay for it, they don't use the official game because they don't want to pay.

People played Turtle because it was a superior experience to the paid official classic offering. It had properly balanced classes, tons of new, high-quality content, real support staff instead of bots with sub-5 minute wait time for service, policing bots properly instead of ignoring them. Blizzard could offer this quality of service but chooses not to.

That seems to conflict with the idea that Turtle's problem was that they charged money for services related to the game.

They will could have shut down the free service but brought the new gameplay to retail.