Why is samara related to karma

Answer: Luck

Explanation: A good Samaritan is someone who does good deeds. it is believed that if you do good deeds you'll have good karma or luck, or if you do something bad you can get the opposite.

If you meant Samsara * it is related to Karma because it is related by definition. An action has an effect (aka. Actions have consiquences.) and repeating an action leads to suffering, it is an example of the cycle of Samsara.