Crystal Field Theory

When I learned about crystal field theory I had fallen on a paradox. When K4[Fe(CN)6] is formed then three d orbitals are occupied by electrons of Fe2+ pairly and the rest two d orbitals are occupied by electrons of lone pair electron of CN-. So when visible light falls on it, the d orbitals are splitted into two sets which are t2g and eg and the electrons of eg orbitals jump into t2g orbitals by absorbing a portion of this light. But my question is that how the electrons of eg orbitals jump into t2g orbitals when the d orbitas are already occupied by the electrons of Fe2+ and ligand during bonding.