Thing is capability machines (like this and the 432 and lots of research machines) were very much the thing at the time - cutting edge even. The research literature was full of them. I did a paper design at the time.

What ate them up was "what can you fit all on a chip with not many pins", followed by "what can you fit along with a cache on a chip with more pins", things move so much faster if everything's on the same die.

Tagged architectures are old, Burroughs mainframes had them back in the 70s along with rudimentary hardware objects (pageable even)