Well, this is just my understanding of it... but TQ introduced new anti-cheat systems that were difficult to keep up with. They changed parameters and mechanisms frequently, and ConquerAI was the only bot that I'm aware of that managed to keep up for a very short time; but only because there was a flaw they were able to take advantage of during their first release of it. Fighting their changes became a very costly effort for what would be only a few days of uptime of the bot.
The question of "what if but for private servers" is a valid one. Anticheat on private servers are (for the most part) a joke. But I think a paid solution isn't really the answer for that. One solution isn't a fit for all. Making the tooling available to make your own bot for a private server seems much more reasonable.