I don't believe Maserati, Bentley etc and the top-end German cars in the 100k-ish bracket that are Tesla S/X competitors share platforms.
I can understand why you don't think that, But they do.
And that other lot. And not just platforms, all manner of components, common suppliers, commercial systems and processes.
From a customer perspective I find a limited model range to be a plus.
That, sir is the key trick. To persuade people buying a VW Golf that they're not buying an Audi A3, a Skoda Octavia, or a Seat Leon. And vice versa, and all permutations in between. But they do share the same platform, many components, yet have some degree of distinct personality. I drive one of those, and have access to a different one owned by a close relative. The "shared platform" concept works, and it works really well.