$10 billions is a pittance, it gives you two thirds of Whatsapp or the entire Skype before it was acquired by MS (adjusted for inflation), so I don't think I'm delusional when I'm saying that it is not a great sum to pay when the future of your entire industry depends on you being best at building EVs (and Tesla now is the best).
I've had the same discussion on places like /r/cars, i.e. that Tesla doesn't sell cars, it sells batteries and the accompanying software (with some wheels attached to the whole thing), while companies like VW, MB or BMW have almost no clue on how to build the best batteries, never mind the best software, they're only good at building cars (and lately not so good even at that), which is an industry on its way out.
[1] https://mybroadband.co.za/forum/threads/tsi-engine-problems....
Outside car manufacturers there's a lot of cashed up companies that would like to take a punt in this space.
Licensing/partnership contracts are often written so that they don't automatically survive changes of ownership, which makes buying into such a partnership by acquisition less than reliable.