One of the possible reasons is that they want to wipe off this traditional crypto exchanges that are not fully regulated and controlled by Governments, and they want to push people into using platforms that they have full control of.
The Idea is to get people to abandon bitcoin which they can not also control and then trade those ETFs on exchanges that Governments can control and manipulate any time they want.
The idea is to control cryptocurrency by controlling the investment through ETFs. For that they would need to slowly destroy the exchanges which after complying to the government boards are still getting charged hefty fines. After sometime these exchanges would halt operations and then the government would use big financial giants to control the cryptocurrency.
What you have said is also correct. I only elaborated it in detail or tried doing it.