Yes, Bet365 is safe to use. The sportsbook provides various levels of firewall and other protections and the sportsbook itself is regulated by each of the state gaming regulations Bet365 is legal in.
The bet365 site also offers casino games, fantasy sports, and plenty more. However, since bet365 is banned in many countries due to gambling restrictions, many people around Europe, the US, and other locations will find they can't access bet365.