It was largely developed by Cray Research, which got bought by SGI, which sold Cray's SPARC Superserver division to Sun for cheap ( < $100M)[0].

[0] https://www.forbes.com/2002/05/06/0506sun.html#703713c16a5e

I sure do... there was someone on YouTube who owned one, he was going to let people use it for giggles, but he seems to have gone AWOL... shame really, because I don't know how else people can get to experience such hardware like this without physical access.

Jim Austin has one: https://www.computermuseum.org.uk/machines/sun_e10000.html