Some adjectives need a preposition before their object. There doesn't see to be a logical rule, I'm afraid! We just need to learn them.
Here are some of the most common ones:
famous for
France is famous for its food.
proud of
He is very proud of his new car.
interested in
Julie is very interested in sport.
pleased with
John is very pleased with his new suit.
bad at
They are very bad at maths.
good at
Einstein was very good at physics.
married to
My mother has been married to my father for 20 years.
excited about
I'm very excited about my holiday.
different from / to
Coffee is different from tea.
afraid of
I'm afraid of spiders.