Why do think this series failed?

I know the films probably weren’t up to the standard of the best Bonds, but this one was a good film.
We see a spy to rival Bond with a strong personality. Though perhaps he was too intellectual and the series was far too realistic. There wasn’t much glamour and gadgets.
I’d like to think they could revive Harry Palmer but as they’ve filmed nearly and unlike the Bond films I can’t see them re-writing the books or creating new stories for him.