Howe pitched Zito not to win the Cy Young award, but to give the A's a chance to secure home field advantage throughout the playoffs. If the Yankees had lost that Sunday, they would have had to go all the way to Tampa to play a make-up game to determine home field, then start the playoffs Tuesday. But the Yankees won and clinched home field advantage throughout.
While that move was definitely sensible and understandable, as it turns out home-field advantage did neither team any good. In retrospect, Howe should have been happy with home field for the DS, and ran out Cory Lidle on Sunday to close out the season and stacked the lefties against the Twins. In a 7 game series (ALCS) in baseball (unlike in football or basketball), home field advantage isn't the deciding factor.
To answer your question, I wouldn't say I blame Howe, but I felt he was clearly outmanaged throughout the DS. Taking just game 5, while it was the offense's fault for not producing, Howe didn't really try to manage or manufacture runs until very late in the ballgame. As the commentators pointed out repeatedly, you don't want to get into a grudge match with the Twins fine bullpen. I think at the very least Howe should learn a few things from Scioscia's smallball. For example, I believe in the 6th inning Howe let Ramon Hernandez ground out weakly into an inning-ending double play. I was hoping to see the non-productive Hernandez lay down a sacrifice bunt with the dangerous Ray Durham on deck, but Howe just doesn't play that way. In a short series, you can't just wait until your stars bang out extra-base hits. And you certainly can't wait for your ice-cold catcher to come around in game 5.
Another move I disagreed with was putting the volatile Billy Koch in there for the 9th. While he was a pretty good closer throughout the season, he's not a 1-2-3 guy and blew more than a few saves. Bradford was doing well, and Rincon was available to match up against lefties. With their offense in such a funk, you'd be happy if the A's crossed one run across the plate in the bottom of the 9th to tie the ballgame. Why waste your closer right there? I understand it's common to leave it all on the field, so in theory you put the closer out there to hold the score. But in this case, Koch is just not one of the ace stoppers in the league yet (i.e. Trevor Hoffman, Mariano Rivera, Robb Nenn), and I felt before the 9th started that it was a risky move. I didn't expect
3 insurance runs though.

This was perhaps a minor mistake in judgment (most managers probably would have done the same) but as it turns out, it was the fatal decision.
On the other hand, I don't fault Howe since it was Tejada who pulled a Barry Bonds' playoff performance. Other guys didn't swing the bat well either, and that's why the A's blew it.