At the end of "The Legend of Sleepy Hollow",the author gives several explanations for what happened to Ichabod Crane. Use specific details from the...

Ichabod Crane was well
known in the community to believe in witches and goblins and the story of the Headless Horseman.
He had a copy of Cotton Mather's book on witchcraft and:

His appetite for the marvellous, and his powers of digesting it, were equally
extraordinary; and both had been increased by his residence in this spellbound region.

No doubt Brom Bones knew about his wild imagination and figured he
could pull off a great prank and get rid of his rival for Katrina's hand in marriage.

There is a lot ofabout Brom Bones and his skill as a horseman, plus Brom told the story
of having escaped the Headless Horseman himself, so he was familiar with the particulars of the
legend and how to pull off such a prank.

He was famed for
great knowledge and skill in horsemanship, being as dexterous on horseback as a
Tartar.

Also, Brom was a big jokester, so it makes sense
he would pull a prank on Ichabod:

He was always ready for
either a fight or a frolic; but had more mischief than ill-will in his composition; and, with
all his overbearing roughness, there was a strong dash of waggish good humor at
bottom. 

and

He was, in fact, noted for preferring vicious
animals, given to all kinds of tricks, which kept the rider in constant risk of his neck, for he
held a tractable well-broken horse as unworthy of a lad of spirit

When Ichabod leaves the Van Tassel farm dejected because Katrina has spurned his
advances, he sees the Headless Horseman at the very same bridge where Brom told his story of
escaping the Horseman:

He affirmed that, on returning one
night from the neighboring village of Sing Sing, he had been overtaken by this midnight trooper;
that he had offered to race with him for a bowl of punch, and should have won it too, for
Dare-devil beat the goblin horse all hollow, but, just as they came to the church bridge, the
Hessian bolted, and vanished in a flash of fire.

When
Ichabod is chased by the ghost, he says:

He recollected
the place where Brom Boness ghostly competitor had disappeared. If I can but reach that
bridge, thought Ichabod, I am safe.

Finally, after
Ichabod disappears, whenever the story comes up, Brom Bones knows more than he is
telling:

Brom Bones too, who shortly after his rivals
disappearance conducted the blooming Katrina in triumph to the altar, was observed to look
exceedingly knowing whenever the story of Ichabod was related, and always burst into a hearty
laugh at the mention of the pumpkin; which led some to suspect that he knew more about the
matter than he chose to tell.