Yeah, the general election cycle isn’t actually too terribly long, and is actually shorter now than it was at one point in history. Right now we hold our Federal elections on the First Tuesday after the First Monday in November.
Long ago, that wasn’t actually the date of the national election. The Constitution provides that Congress has the power to set uniform election dates–but it is not required to do so. Initially the rule was simple: states had to select their electors at some point by the first Wednesday in December–the date the Electors were required to meet and cast votes (note they didn’t meet centrally in Washington and never have, they meet on a state by state basis) but no more than 34 days prior to said date in December. So most States had their electors chosen some time in November, but the specific date varied from State to State. Remember too that the mechanism of selecting electors varied as well, with some states allowing a popular vote (among the much more restricted franchise of the time), while others chose electors by the State legislature.
This situation persisted until 1845, when the current election day was set by Congress. One issue that had arisen is that gamesmanship of various sorts could occur as politicians in states that selected electors later could adjust their choice based on how other States had voted.
The primary elections must be understood as not being part of our actual election system at all. They are such a mess for historical reasons. But the way it used to work is there wasn’t a primary season at all, there was just a convention date. Power brokers in each state would work out who the delegates would be and they’d be selected with no real input from ordinary voters. Often times a single very powerful party boss might control a huge slate of delegates who were loyal to him and would vote how he asked. Then they would all meet at the national convention, usually vote many many times, and then walk away with a party nominee.
When primaries were first developed they were strictly preference polls. These are just elections to express opinions–they have no real power. It sounds goofy, but believe it or not there was a history in the United States of conducting preference polls on various issues. This was before the age of the modern day pollster, and in fact many preference polls were sponsored by newspapers, people would literally show up, indicate their preferences, and the newspaper would run the numbers. This would create information on the “general feel” of people.
Since party primaries were just preference polls, why would they need to be worried about a “schedule?” Who cares if one state does it in January ten months before the election? These preference polls have no meaning. Who cares if another state does it a week before the party national convention?
Now, the caucuses are a remnant of the old “party power broker system” except they tend to be more democratic today, in the old system local political bosses would largely determine the outcome of caucuses or they would determine the slate of delegates who would be beholden to the wishes of the party boss, not any low level party members who happened to vote for him at the caucus. But they are also ran asynchronously. But the reason for that is because under the old system no one was really paying attention to the caucuses–it was understood an immense amount of horse trading, fighting, and politicking would have to happen at the convention for any decision about a nominee to be made. So why cover the caucus process? It h as no real bearing on what happens at the convention because the tight-lipped party bosses aren’t going to significantly telegraph their intentions, and even when they would their intentions would have to meet reality at the convention, where they may have to acquiesce to supporting a different candidate. So there was no coordination of timing of the caucuses because there frankly didn’t need to be–the timing of them wasn’t important so no one cared to try and synchronize it.
Where things got off the rails is when we made the primaries “largely binding”, and made even the caucuses binding/more democratic in almost every state that still does caucuses. This meant this long schedule of asynchronous events had real importance now, as each state’s outcome represented a generally irrevocable acquisition of support at the convention. Other things were also done to deemphasize the convention–for example in the 1800s and early 1900s a nominee was actually required to get a supermajority of delegate support. In a “primary election” system, any real contested primary would make that very difficult. For example Obama, Romney, Clinton ('92–likely '16), Dukakis, even incumbent President Jimmy Carter, would not have hit the supermajority threshold of delegates and the conventions would’ve all been contested.
So basically the system developed organically, and the schedule was “too set” by then to be easily changed, because now each state had learned there was certain value in certain positions on the calendar. Further, the electorate and politicians had quickly adapted to the “winnowing” style of primary where you start with a big slate and narrow it down, and the impetus to change that was small. There have been steps towards that, for example Super Tuesday as a concept developed out of a deliberate desire to make the primary season more compact, but it’s been a mixed bag. For example in 2008 the Democrats had a Super-Super Tuesday where like 21 states voted, that could’ve been seen by some as a trend towards a true “national primary day.” But the trend didn’t hold, Super Tuesday this year obviously the Democrats only held contests in about half as many states.
I frankly think voter-selection of party nominees is a problem, and promotes incorrect ideas about how democracy should work. Virtually no other democracy does this, and they all work fine without it–arguably they produce better candidates than we do.