At that time, memory was still quite expensive per bit, so the bit-mapped display approach was economically infeasible. Instead, the video display used a display program, which was a list of commands to the hardware of the display (often stored in main memory).
The commands were to do things like display lines (often called 'strokes'), points, etc, at arbitrary locations (and angles, for the lines) specified by the command(s). The commands might also include attributes; things like dashed lines, bold, etc. The display processor converted the commands to voltages sent to the beam controls of the CRT (both location and intensity), to draw the needed strokes/etc.
Some graphics units included a character generator, so the commands might include text displays. (Although characters could be drawn using display commands, using a character generator saved commands, which might be limited in total number.)