Why does a year last the same time as the four seasons ?
Long before we had any serious science of astronomy, we had seasons. We defined a year as being four seasons. All you need to do that is long term memory.
Once you can count and record events in some way, you start counting days.
As we accumulated knowledge of the stars, we noticed that the changes of positions of the stars in the heavens followed very regular cycles. That gave us a way to relate a year to an exact number of days ( and in fact to a fraction of a day ).
When we developed physics enough to be able to associate the yearly cycle with an orbital cycle we changed our definition of year to be exactly that cycle ( and we even allow for slight changes in that's cycle's length ).
So we invented the approximate year first and then refined it to match our understanding of physics.
The seasons could take 100 days or 200 or 20 years (aprox. like in GoT)... but exactly (exactly???) 1 year. Why?
Because a year happens to be the period of time that matches the changes in seasons and heavens we first noticed and first gave that name.
We've just refined the definition a bit more.
After some thought I've edited my original to include a reference to the Egyptian Calendar which has three seasons ( winter, summer and inundation ), so four seasons doesn't have to be the number. It is notable that the approximate year length seems to be the same. I dare say other similar examples are out there and unknown to me.