Tesla was never an important customer for Mobileye. Even with Model 3, volumes were going to be low in comparison to all their other, much larger auto manufacturers. Soon after working with Mobileye, it became apparent that the two companies differed on strategy. Tesla saw that Mobileye wasn’t going to improve their offerings quickly enough for them, and even worse, when their offerings did finally improve, it would allow all Tesla competitors equal AP parity with Tesla.
So Tesla soon started a parallel effort to create their own AP chipset so that they could get V2 of AP out well before the rest of the industry had it. For their part, Mobileye saw someone who could directly compete against them, was being irresponsible with their chip, and just wasn’t worth anything to their bottom line. Tesla and Mobileye then had their demands of each other that neither side wanted to give. Raw video from Tesla, and access to raw data streams from Mobileye. So Mobileye cut them off. This caught Tesla completely by surprise and effectively forced Tesla to sell new cars with no working AP for quite a while.
That Tesla managed to shrug off this seemingly major problem is a testament to Elon’s agility and his BSing talents.