They're obviously selling Benzema and they want to re-invest some of the money on another profilic striker. Gila was unstoppable against Lyon in CL (i think he scored 3 times against them), he's the serie A topscorer and that probably made Lyon think that he's worthy of 25m eur.
Currently it looks like Fiorentina doesn't want to sell him, even though selling him will mean a ~10m eur profit on Gila. (they bought him for ~15m eur)