Well that theory is that it's competitors (other auto manufacturers, etc.). I think that certainly comes into play, but I think the bigger effect is from the big funds who benefit from major swings in the price.
Why do I think that? Think about all the *positive* media Tesla was getting when the share price was running up. There seemed to be a lot of that, and very little FUD.
If the theory you posted was correct, the media would always have a negative bias. But during the big runup, the media seemed to be assisting the upward movement. (At least that's how I remember it--maybe I am wrong).
Since the media seems to assist in pushing the price down to a minimum, then helping it up to a maximum, it lends more credence to the MMs being the true influence here as they profit most from the movement in the extremes.
And it's another hint that we'll be running up soon.