They see Tesla being a trillion dollar company. SONY was busy laughing with the media the past 5years.
Re the "Sony Car", isn't it more of a proof of concept of their autonomous sensors. I recall the article mentions 33 for the car they were "showcasing".
Since their strengths lie with camera sensors, my guess is they are just showcasing that theirs work inviting other manufacturers to work with them to "level up" their cars.
If they will go into car manufacturing, they are more likely to partner up with an existing car manufacturer rather than start from scratch.
But that's my guess.