and also the variation of numbers of predators (wolves in the case of snowshoe hare i think) did not explain the variation of hare population in a straightforward way. i suppose these are difficult questions because nature is not simple. there are so many things that can affect other things so it is "web" where everything is linked to every other thing.
i guess these interconnections in animal world are like weather which has turned out to be a chaotic system in the long perpective. in the '70ies it was still believed that there were 7 or so variables which determined the weather and that it would only require enough computing power to solve the equations which link these variables. in the '80ies it was discovered that this is not the case: it's a law of nature that it is actually impossible to predict weather precisely in the long run. the butterfly-effect was used to depict this chaotic feature in the weather: a butterfly hovering its wings in the rainforest in Brazil can cause a hurricane on the other side of the world.
when meteorologists make their calculations more than once with their best models and fastest computers they get different answers every time. --i think that this is what they actually do: they make calculations with different models, compare the results and then decide what kind of weather they predict. the predictions nowadays are actually very good in short perspective, but a week ahead or more it gets more and more uncertain.