Because Johnathan Chait gave such a nice summary:

It was probably just a matter of time before DeLay got nabbed for something or other. The hallmark of his career lies in pushing previously known social, ethical and legal norms further and lower than anybody else had ever had the guts or the indecency to push them.

Congress has always run something of a protection racket, but only DeLay was blunt enough to divide Washington's special pleaders into "friendly" and "unfriendly" camps based on their donations and to invite them into his office to see the lists. It's a tradition for the majority party in the House to run roughshod over the minority, but DeLay has taken majority tyranny to an extreme   wantonly changing voting rules and forbidding Democrats from reading or debating legislation. Gerrymandering is a hallowed American tradition, but DeLay was the first to hit upon doing it without the cover of a census.