Outline briefly two explanations of what really happened with respect to the three wishesThe Monkey's Paw by W.W. Jacobs

The sergeant-major who visits the Whites one cold and
snowy night tells the family of a monkey's paw that has had a spell put upon it to prove
the immutability of fate.  When he tosses it into the fireplace of the Whites, Mr.
White, who has earlier been reckless in his game of chess, retrieves it; then the
soldier leaves and the monkey's paw belongs to the
Whites.

Despite what the soldier who has been in many lands
has told them, Mr. White and his son Herbert do not consider the talisman as genuine or
as possessing any powerful properties.  In fact, Mr. White smiles "shamefacedly at his
own credulity" as he holds up the talisman; his son poses with a solemn face, but he
winks to his mother and sits at the piano striking a few ominous chords.  Clearly, the
first error in judgment by the Whites is in considering the monkey's paw as a fake. 
Therefore, Mr. White does not seriously consider that his modest wish will come
true.

In "The Monkey's Paw" by W. W. Jacobs, the characters
who own the money's paw do not truly believe that it holds magical powers;
consequently, Mr. White is rather frivolous in making the wsh, not pondering seriously
upon his wish before rather rashly forming it.  Secondly, Mrs. White does not consider
the consequences of her wish that Herbert White be brought back from his untimely death.
All in all, because the Whites (1) do not initially take the monkey's paw seriously, and
they do not ponder and plan their wishes sufficiently, and (2) they do not consider all
the consequences of what it is for which they wish, they meet with a tragic
fate.