The major problem, IMHO, was the licensing of C-Kermit. Yes, if you used C-Kermit and set it up properly, it was as fast or faster than ZModem. However, ZMode

The major problem, IMHO, was the licensing of C-Kermit. Yes, if you used C-Kermit and set it up properly, it was as fast or faster than ZModem. However, ZModem had free implementations and was relatively ubiquitous. Columbia University was trying to use the license terms to extract enough money to maintain and improve C-Kermit. Compared with Zmodem or Ymodem, it wasn't a success. At least, that's how I remember things.