His conduct with the whole clinton investigation and seeming to stall with answering Congress (even behind closed doors) is certainly questionable and the thing with overblowing the emails that got leaked to Anthony Wiener (by accident apparently, via an auto forwarding thing) and seeming to lie to congress is certainly a no no.
Still, Comey's conduct aside, we still have to consider the fact that there is an investigation going on and it's unknown whether he was fired because of that or what. Obviously, firing him won't stop the investigation neccesarily.
For what it's worth, my theory is he tried to look above-it-all and satisfy everyone. So he decided against charges, but complained about Clinton, hoping he'd attract the support of people who thought she was suspicious but not criminal. But of course, since no one was voting for him, only for one of the two, not picking a side directly cost him.
Meanwhile, it looks like news agencies are sizing up the font they are using to report on his firing, so they think this is big news.
In context, it IS big news, because the President firing the FBI director is normally a thing that does not happen. If the FBI wasn't doing an investigation on Trump stuff, it'd be somewhat less of a big deal, but they are doing an investigation.
What the WH does NEXT however, is going to be closely watched.
Also, apparently Congress had virtually no notice at all that it was going to happen, the leaders may have gotten a bit, but it surprised everybody.