It is their own Adobe Flash and it’s good that it is faded out. Too obscure in modern times, too many security flaws. Only warm nostalgic memories will remain in 10 years.
While true it was their actual flash, based on install basis and history, silverlight was a blimp on MS history. While flash died slowly off after 2008 as html5 gained ground and plugins fell out of favor (anyone remember java applets?), MS decided to launch their own Plugin into a world that already turned away from this technologies. Classic MS.
The comparison that VBS is like MS JS is a bit wonky, as JS is breathing and alive, while VBS is not. You also never encounter VBS on a website.