I think the valuation is driven by the delivery vans rather than the R1T.
The world desperately needs electric delivery vans. Rivian already has Amazon as a customer and as an investor. That's an outstanding combination.
The R1T is a super heavy, niche pickup truck for wealthy American households (DINK?) who like camping in style. It's not a truck for the industry, and it will not come close to the F150 in utility.
I totally agree the Cybertruck is a design from a comic book and I have no idea how it would pass pedestrian safety regulations. But the Cybertruck being a bizarre vehicle doesn't imply there's a big market for the R1T.