VW is good at making cars, but bad at software. They’ve had to delay the introduction of new models (Golf, ID.3) because of software issues. Rivian has sort of the opposite problem: their production lines sit still often because of problems in the supply chain.

Volkswagen has the expertise to solve Rivian’s production and supplier problems, and the cash they will need to survive and develop some cheaper models (the EV market is stagnating right now for a lack of budget options, and Rivian only sells trucks and SUVs). And they’re hoping Rivian software engineers can help them fix their software woes.