You may want to learn what the word explanation means

As well as some other words, for that matter. It is not about what you think it is, it is what the party which you explain something to thinks about your words and whether they consider it as an explanation. So far I don't see how you can coherently explain why the mining cartel is going for Bitcoin Cash (or whatever) unless they want to outcompete Bitcoin. And this addressees your next question regarding other altcoins. They are there to earn profits for their developers (let's assume that for a moment). But in case of Bitcoin Cash this is only possible if it manages to bring down the "regular" Bitcoin. Otherwise, it will fail itself. As simple as that. And that specifically poses the question before you why they (the mining cartel) would deliberately want to create a coin which is set to fail. In other words, if you want to explain something, you should make the ends meet in your "explanation" (which you don't)