Why is selection more efficient in larger populations

Compared to smaller populations why is natural selection considered to work better in larger populations, Is it due to the presence of more differences among the population ? but why isn't selection considered to help fix characters faster in smaller populations just like drift ?

Good one, man. That's very true. A population should be able to be modified easier by selecting events if it's smaller. The problem is when a population's trait is selected against it cuts the population and the genetic diversity. The population wouldn't be able to change very much if there wasn't a large stock for natural selection to start with. The more diverse the genetics of the population, the more they'll be able to adapt to selecting events.

There's more to this, but that explains one aspect simply.