In Chapters 5-7 of Animal Farm, what causes the animals to struggle with breaking up the stones for the windmill, and what is the outcome?

One of
the main problems the animals run into when constructing the windmill is how to break the
massive pieces of limestone into suitable sizes. Initially, the animals thought there was no way
to break up the stone without the use of picks and crowbars, which were impossible to use
because no animal could stand on their hind legs or correctly wield the human tools. Eventually,
the animals decided to use the force of gravity to break up the stone by hauling large slabs of
limestone to the top of the quarry and letting them tumble down to the bottom of the quarry,
where the slabs would break into smaller pieces. Once the limestone was broken into smaller
pieces, they would load the stone into carts and haul it back up the quarry.

The only issue with this method is that it is arduous, taxing work, which exhausts ,
who does the majority of the heavy lifting. The animals are able to retrieve the necessary
limestone to build the windmill, and they eventually finish construction. However, Boxer uses
all of his energy hauling the stone and eventually exhausts himself.