Seeds sown very deep in the soil fail to germinate because they
cannot exert enough force to push the soil upward
do not get enough oxygen
Seeds sown very deep into the soil fail to germinate because they require oxygen to germinate. At those depths, enough oxygen is not present in the soil. This is why soil is ploughed before seeds are sown. This helps to aerate the soil.
Also at such depths, the shoot will struggle to push through the soil.