The electronic configuration of Fe is 1s2 2s2 2p6 3s2 3p6 4s2 3d6. So after removing two electrons the configuration becomes: 1s2 2s2 2p6 3s2 3p6 3d6

But why cant the electrons rearrange themselves to give a more stable 1s2 2s2 2p6 3s2 3p6 4s1 3d5 configuration?

The electronic configuration of Fe is $\ce{[Ar] 3d^6 4s^2}$. So after removing two electrons the configuration becomes: $\ce{[Ar] 3d^6}$

But why can't the electrons rearrange themselves to give a more stable $\ce{[Ar] 3d^5 4s^1}$ configuration?