Answer:
Carbon is generally stable across a variety of oxidation states like +4, -2, 0, and +4. While Pb is generally only stable in the +2 oxidation state
Explanation:
There are two main reasons for this, first is the increase in metallic character as you go down the group, this tends to increase the stability of the +2 oxidation state over the +4 oxidation state. A good example of this is the oxides of lead. Pb can form two oxides PbO and PbO2. PbO, having an oxidation state of +2 is much more stable than PbO2 with an oxidation stae of +4. PbO2 will readily decompose to form the more stable PbO. This is due to the inert pair effect, where Pb tends to hold it's S shell electrons closer thus making them harder to pull away, thus making the +4 oxidation state difficult to form.
I realize this probably isn't the simple explanation you were looking for, but the question itself is a complicated one to explain
