If one stock goes up/down, the other does too. This has happened repeatedly with these two companies specifically, even.

This should be easy to prove that their correlation to one another is significantly more than to the market, or maybe more accurately to tech stocks as a whole. do you have these numbers or is it just speculation?

The other poster makes a much stronger argument, pointing out how some investors in Tesla are concerned about musk having to sell stock to support x, which could lead to a fall in x prices.