Yes, it is safe to buy crypto in Robinhood. The platform is registered with FinCEN as a money services business implying that it is subject to and complies with all the applicable requirements of the Bank Secrecy Act. Robinhood also complies with the applicable money transmitter laws for US states.
Robinhood has also implemented several security measures that make it a safe platform to buy crypto. For instance, the platform uses two-factor authentication (2FA) to keep user account safe and have adopted Federal Deposit Insurance Corporation (FDIC) insurance. Robinhood also stores its crypto assets on cold storage.