About 3 million TI-99/4A computers were sold. The C-64 (based on the 6502, but with 6 extra I/O pins) sold around 17 million units (best selling computer model of all time). The VIC-20 did about another 3 million on that.
The 6502 really was the dominant processor of the time. The Z-80 was around, but was outsold about 6 to 1 by the 6502 cores.
Wan’t the Z-80 used in microwaves and other appliance for years?