Can you please elaborate? I get that he brought maybe a couple of dozens of people from Prism to Microsoft, but I can't see why that brought down DEC, especially it was DEC who paused Prism.

I also know that some Prism code was used in NT but again I hardly see why that brought down DEC.

That could be the cause, if DEC had some competitive hardware or software projects, but none that I know so far. Please share your knowledge with us.