According to the theory of natural selection why are some individuals more likely to survive and reproduce if they are better adapted to their environment

Well lets give an example. There are brown bunnies and white bunnies in an the same habitat. One day, it snows. The brown bunnies are gonna be obvious and out in the open snow for predators to find and eat. The brown bunny population will decrease while the white bunnies will all survive. The white bunnies will reproduce naturally, but the brown bunny population is decreasing so there are not that many bunnies to reproduce. The white bunny was better adapted to a habitat filled with snow so they survived and reproduced. On the other day, lets change the scenario and say all the snow has melted. The dirt is now exposed. Well, dirt is brown so the brown bunnies are now able to blend in with their surroundings. The white bunnies will be a little more obvious and the predators will find and eat them. Now the white bunny population is decreasing while the brown bunnies are surviving. The brown bunnies will reproduce and increase their population once more. However, the white bunnies are all being hunted so there are not that many white bunnies to reproduce. The brown bunnies were better adapted to a habitat with dirt because they are able to blend in and as a result they survived and reproduced. Of course, snow is going to fall once more and the scenario will be the same as the first. The cycle continues on and on. I hope you understand. I typed all of this really fast and do not really want to go back and read it so there may or may not be typos. If there are typos, I hope that doesn't affect your understanding. Please feel free to comment if there are any questions that you may have. Have a nice day!