That's a simplistic unerstanding that ignores the actual technology. Expert systems were nothing more than logic programming dressed up to seem all "ai". Prolog

That's a simplistic unerstanding that ignores the actual technology. Expert systems were nothing more than logic programming dressed up to seem all "ai". Prolog is backward chaining, while Clips expert system shell is forward chaining. Today they are referred to as business rules engines, which can again be forward and backward chaining. Sql databases are also in fact logic programming, basically prolog without recursion and iteration, but instead have pl-sql and t-sql to make them turing complete. Also, with triggers they are also forward chaining too. The main difference between crud and expert system is essentially that crud is multiuser and everchanging, and so is actually a better version of classical expert systems.