Why was the boy crying at the end of the story in The Old Man and the Sea?

Santiago is Manolin’s mentor. Manolin idolizes him and
pities him at the same time. To Manolin, Santiago is a father-figure. Father-figures and
mentors are initially perceived by their admirers as invincible. Eventually, they are
dethroned. This changes the relationship dramatically. Manolin still admires Santiago
but he, and Santiago, must endure the other fishermen’s ridicule. Manolin’s loyalty to
the old man has replaced his unwavering admiration.

When
Santiago returns with the half-eaten marlin, he has succeeded and lost. This parallels
Manolin’s concept of him as a fallen hero whom he is still loyal to. Manolin cries
because he empathizes for the old man who had been in a slump. He finally caught a great
fish only to lose it to the sharks. The other fishermen recognize the greatness of the
catch, but it is still a failure because the fish is not intact. The half-eaten fish
symbolizes the old man: a distorted and lesser version of its (his) former
greatness.

Although Santiago reclaims his public
respectability as a fisherman, Manolin cries because this success was also a defeat. It
is a further dethroning of his idol. Manolin remains loyal but also recognizes that
mentors and father-figures are destined to be dethroned and there is a loss of innocence
and naivety that comes with this realization.