Cui bono is a Latin idiom.
The construction is called "double
dative." (Dative is generally
the case for the indirect object,
but there are other uses.)

Bono of course means "good,"
and it's Dative of Purpose or Tendency.
So if Lilly Wilson translated it,
"[like,] good," she'd be, like, right.
Cui is the dative singular of

the interrogative pronoun
and it's dative of reference-
"to whom," or "for whom,"
with a question mark.
So the phrase entire denotes

something being, like, good
for somebody-but for whom?
The implication is that when
you want to figure out who's
responsible for something,

the first question to ask is
"Who benefits?"
There are still a lot of
question marks around
the attack on the Twin Towers.

But can anyone deny
that September eleventh
was the best thing that could
possibly have happened
for George W. Bush?