I propose to start from the very beginning and smoothly move on to a possible justification for their current state.
According to the official versions of history, all the megalithic ruins are successfully attributed to the Inca civilization. However, even with a cursory examination of the photographs, this moment can be called into question.
For example, Wikipedia kindly presents the dimensions of 2 slabs, which are laid in the base of the destroyed structure. The first weighs 131 tons and the second about 85 tons. The slabs described in Wikipedia are made of red sandstone and were mined in a quarry nearby (10 kilometers).
Unfortunately, I did not find photographs indicating specifically these plates, but they should approximately look like this.
Now imagine how the primitive Indians could cut and move such huge blocks. Only for such work it was necessary to use almost all the resources of the Incas.
But I cannot take this as convincing proof for you, since with the help of great efforts the Indians could still do it.
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But the processing of andesite on an industrial scale with such precision the Incas in technical terms could not master.
Here are a couple of examples of incredible processing.
Thus, we can conclude that the Incas have no involvement in the creation of these megaliths. As a result, we get the ruins of buildings of an ancient unknown civilization. Judging by the level of construction, we can talk about a highly developed civilization.
The level of development of that civilization can also be judged by some constructive decisions on the blocks. Here are a couple of examples.
So what happened to that civilization?
Go back to the top of the page and carefully review the photos that cover the area around. They show traces of total destruction, which scattered multi-ton megaliths like fluffs.
And if you look closely, they were not only scattered, but directly torn to pieces. Such an impact on the stones could have produced only 2 possible events.
It was either a cataclysm of incredible scale, or a weapon not inferior in the degree of destruction to modern ones.
Since we are talking about a likely highly developed civilization, it is hard to believe in the version with a cataclysm. I think so, because even polygonal masonry is often made for earthquake resistance.
That is, that civilization perfectly understood where it was building structures, and knew how to deal with the attacks of nature. This means that we have only one option for the turn of events.
Once upon a time, structures in this area were attacked by unknown and powerful weapons. The ruins of megaliths are very similar in nature to the result of explosions.
Of course, I do not pretend to be the final truth, but this version seems to me logical and quite reasonable.