Why were the moon missions stopped?

The short answer: Cost

The better answer:The Apollo program was the vision of a nation put forth by a leader that was shortly there after assassinated.

His vision kept the massively over budget program funded.

Some people saw it as an adventure, not science or the way to save our planet and our race.

After the successful landing the government no longer saw the need for further trips to the moon.

One of the most shortsighted things I have ever heard of.