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[I]f politics were NOT distributed this way, say it was more like 70:30, then would politics even need to exist in the first place?

Why don't you look at the split between Democrats and Republicans from 1933 to 1970 or so (not that that's the only period in American history where one political party dominated the other).
The 50/50 split is not a matter of statistics but of sociology, and is a feature of two-party systems. In such a system, it is a bad idea to focus on issues that have support from only a tiny minority, because the opponent will pounce and easily capitalize and take the much more popular position. So in a two-party system, political discourse is often dominated by wedge issues over which the populace is divided roughly 50/50. You can see this in other two-party systems as well, such as Brexit in the UK during the previous general election. Wedge issues shift over time: the Republicans in the US have moved away from homophobia as the acceptance of homosexuals has steadily increased, and shifted towards transphobia.
The dynamics is very different in multi-party systems. In such a system, it can be beneficial to focus on minority issues and interests, if there is a small group with strongly held beliefs. For example, in the Dutch national parliament there is a party that supports a literalist interpretation of the Bible, including support of the death penalty (which is banned in the EU), even though only 10-20% of the population regularly attends religious service. There is also a party focusing on animal rights, and an openly anti-Semitic anti-immigrant party. In a two-party system, such fringe movements would not survive. >

Go back further in history. Or to other elections that aren't nationwide. There are plenty of landslides, and politics still existed where and when that happened. >

If one side had a huge majority, they would likely begin doing things that tested their popularity. The minority party would also adapt to hold more popular positions >

I think it has more to do with the two party system. If we had a parliamentary proportional system, then different groups would need to make coalitions and there would likely be more bipartisanship. As it is now, the extremists can hijack a party and force the rest of the members to follow along.