I did read they think Cradel Cap could be caused from a hormone released during pregnancy. But they are not really sure, seems very hard to determine exactly what causes it. One thing is for sure its NOT from your baby being dirty like some older people will say.
My DD got it fairly young and the only way that worked for her was to wash her hair every night and brush with a soft brush / comb each morning.
Other mums in our group found that putting oil or sorbelene cream on it over night then gentle brushing / scraping it off in the morning worked. Some babies kept getting it over and over, just horrible.
Best of luck. Keep trying a few different things, you'll come cross what works best for your baby.
DD is 3yr 8 months - DS is 6 months