The firings were not the offense. They were the clue that suggested the offense.

Words of Joshua Marshall at Talking Points Memo carefully explaining the difference between the usual firings of prosecutors by presidents and this purge:

First, is this about firings? Kinsley is still mulling over whether this is comparable to Bill Clinton's entirely normal dismissal of US Attorneys when he came into office. Would it be as big a deal if the Bush White House had fired all the US Attorneys at the start of the second term, as folks at the White House first seemed to have considered?

The firings were not the offense. They were the clue that suggested the offense. As the Congressional Research Service has shown, over the last twenty-five years only ten US Attorneys have been dismissed other than at the beginning of a new president's term of office. And of those eight were for clear cause. For instance, one of them bit a stripper on the arm in a night club. And that, not surprisingly, led to his ouster.

To quote the CRS report ...

In virtually all of those 10 previous cases, serious issues of personal or professional conduct appeared to be the driving issue. Prior to December, for example, only two U.S. Attorneys were outright fired for improper, and in one case criminal, behavior. The CRS report identifies six other U.S. Attorneys who resigned during the 25-year period who were implicated in news reports of “questionable conduct.” For two others, the CRS was unable to determine the cause.

(For more details on this key element of the firings story, see this discussion by Scott Lilly.)

In any case, ten times over twenty five years and in eight of those cases for clear and publicly aired reasons.

And then on one day, secretly and with no explanation, seven get canned. And several are involved in corruption investigations targetting Republicans. The first public explanation is that they were fired for poor performance. But then it turns most were among the highest performing US Attorneys in the country. Add in the fact that one of the eight was overseeing one of the broadest ranging and historic public corruption cases in US history and ... well, it all got our attention.

Then, only a little digging revealed clear evidence that two of the US Attorneys were dismissed for not pursuing bogus claims of Democratic 'voter fraud'.

Update: And in another post, Marshall states it again very clearly: (my bold)

This isn't about the AG's lies. It's not about the attempted cover-up. It's not about executive privilege and investigative process mumbojumbo.

This is about using US Attorneys to damage Democrats and protect Republicans, using the Department of Justice as a partisan cudgel in the war for national political dominance. All the secrecy and lies, the blundering and covering-up stems from this one central fact.