+ 2 oxidation state of lead is more stable than + 4, because of

IV A group elements
Common oxidation state is : "+4"
C shows :- +4 -4
Si:- +4 [Stable]

Ge, Sn;-  +2,+1,+4(stable)

Pb:-    +2, +4(stable)
→ For Ge, Sn +4 is stable oxidation state hence in +2 oxidation state they acts as reducing agents
→ Where as for Pb +2 oxidation state is state [due to inert pair effect] hence in +4 oxidation state Pb acts as oxidising agent
→ Higher oxidation state is due to involvement of ns and np electron
i.e., ns² np²  $\to$  +4
Lower oxidation state is due to involvement of only np electron
i.e., ns² np⁽²⁾ ⇒ +2
Higher oxidation stable stability dececreases from top to bottom
 

Lower oxidation stability increases from top to bottom
Ge⁺² < Sn⁺² < Pb⁺² Stability order