Prosecutors were booted for political reasons.

Paul Kiel of TPM Muckraker:

In other words, the pressure to replace the prosecutors did not come from the people who would know about the U.S. Attorneys' job performance (their supervisors at the Justice Department), but rather from power players in the White House or Republican Party. That would explain why the seven federal prosecutors purged in December were not given a reason for their dismissals -- and why justifications for the firings have sounded like lame rationalizations.

This fits, of course, with McClatchy's finding last week that the Bush administration, in a break with the practice of prior administrations, has been placing conservative loyalists in U.S. Attorney spots across the country. Instead of nominating local, qualified attorneys whose philosophy jibes with the administration (as was the traditional practice), the nomination of U.S. Attorneys has been subsumed into the Republican Party's political machine. Apparently the title of U.S. Attorney is just too attractive a resumé-fattener to dole out helter-skelter. And while you're fattening the resumés of possible future stars of the party, it can't hurt to knock out a prosecutor who was doing considerable damage to the party.