I think the ban on Facebook has little impact on cryptocurrency. but it is not only for facebook. If you think overall impact, then you will see some reason:
1. The increase of Fake/SCAM ICO
2. Losing of trust after been hacked
3. Lacking of proper educational knowledge of crypto
4. Instead of proper awareness, ICO company involved in Investment advertisement.
5. Due to the increase of So many coins.
etc.
Thanks.