The EQS is aerodynamically very efficient designed. This helps a lot with its range. That doesn’t automatically mean that Mercedes knows how to put together an efficient EV.
Aerodynamically they have more than enough talent and it is quite an important factor.
But when we talk about vans, you can forget about aerodynamics. And how good are the Mercedes engineers? Rivian’s engineers are likely not so impressed with the knowledge/skills of the Mercedes engineers when it comes to efficiency in the EV part.
Or that Rivian has no desire to train Mercedes engineers in that area. But it’s just a matter of guessing what’s really going on. Mercedes is a major player and their vans have a good and reliable reputation. Rivian doesn’t have it or doesn’t have it yet.
I watched a documentary series about 2 years ago where Evan McGregor and his best friend ride 2 electric Harleys from the southernmost tip of South America to Los Angeles. Something like 23,000 kilometers over a lot of very difficult terrain, different altitudes and climates. Their support team used 2 Rivians.
Both Rivians continued that journey very well. Only due to pilot error, 1 of the Riviani suffered some damage. Rivian therefore knows what to do to be extremely reliable. They really don’t need Mercedes for that. Perhaps those particular Rivians were designed less profitably than current models, I neither deny nor confirm, because I don’t know.
What was clear was that once the following crew got used to the (im)possibilities of those Rivians, they were very enthusiastic about those vehicles.