The succint answer would be they were choked out of existence in the office market by IBM.

They had an early lead and captured word processing, IBM had big iron and expanded down to personal computers suitable for office word processing and had the big government | military | banking contracts to force through sweeter deals on the desktop range as a "one shop" solution for everything computing related.

Does that mean the trademark is now free and I can start selling Wangs to people?

Hmm, dunno, we've got those in town: https://youtu.be/a64XBWtGuGc?t=43

Founder Dr. An Wang set up the company to have tight control of the stock via his family. He elevated his son, Fred, to president.

While Dr. An Wang (https://en.wikipedia.org/wiki/An_Wang) was a genius and pioneer in computing, his son was not up to the task of running the company and the coming PC revolution caught him flat footed. The company never really recovered.

https://tedium.co/2017/02/14/wang-computers-history-demise/

They kinda did, they sold some minicomputer stuff and also standalone wordprocessors even in the Netherlands. I played games on the one at my dad's work. They just didn't pivot to the PC age as others have mentioned.

The best thing to come out of Wang that everyone used in All PC clones between late eighties and late nineties were SIMMs.

Single in-line memory module https://patents.google.com/patent/US4656605