I believe that 3DRealms was a company that talked about how working for them was different because they had none of the attrition that other companies were having during the Dot Com Bubble burst. But the lack of products, combined with a decline of the gaming economy, did not help this company. Duke Nukem 3D provided many hours of entertainment for me, particularly after I learned how to hack the CON files.
Of course, it's obvious what really happened. Duke was abducted by the Rigelatin forces again while writing his new book, "Why I Will Be Great Again", and 3DRealms has been covering up the abduction. Now, all of the 3DRealms people have blasted into space in search of Duke, and that's why the company seems to have disappeared.