It was originally a JAG spinoff
When NCIS first started, it wasn’t pitched as a separate script with an original idea. It was formed from the popular TV show JAG. In season eight of the CBS Naval legal procedural show, there were two episodes titled “Ice Queen” and “Meltdown.”
CBS
They introduced the new team from NCIS and acted as a backdoor pilot for the show. They show was only taken seriously when it was received well by audiences and a new CBS show was born.