The experiment is not designed well. I would guess that the tameness comes from the non stimulating environment more than the process of selection. It is known

The experiment is not designed well. I would guess that the tameness comes from the non stimulating environment more than the process of selection. It is known that mother imprints a lot of hormonal/stress activities to children while pregnant. Just like starving pregnant mothers have an effect on generations that come through hormonal gene activation similar thing happens to animals in wilderness. Is there a line of foxes bread for generations in captivity with purely random selection?