The show began - in terms of richness of setting and portent, grandness of mythology, and demanding continuity - about as well as a genre series can. In Carnivale's case the genre, loosely, was allegorical fantasy, historically set in the Depression. (It was to have culminated in 1945 after six seasons.) I'm sorry to say that, watching it of late, it's easy to see why the series was cancelled: it really is off-puttingly dark and slow-moving, and it does lean so heavily on its mythology that the character relationships never get time to amount to anything. The Bearded Lady has a touching, perverse relationship with Lodz (the blind fortune teller, one of many high-functioning psychics in the Carnivale) that's always pleasurable to see, but it functions largely as window dressing, a sidelight during the ongoing, markedly less compelling Tale of Ben Hawkins (and That Evil Priest).
Clancy Brown's menacing performance as Brother Justin would have been a marvel if the intricacies of Carnivale's plot didn't have such a chesslike quality; while it's interesting to see him go from good works and social conscience to outright murder over the course of two seasons, his sermonizing and social work never quite enrich his character the way they're intended to - perhaps because the weight of Prophecy and Destiny is so heavy throughout the show. In the Season Two finale he has an exchange with Samson, who says teasingly, 'Small world.' Justin replies: 'Yes. And getting smaller all the time.' Unfortunately for the show, the line works on two levels: the world of the narrative seemed to want to expand throughout the second season, but the focus on Ben and Justin remained static, meaning the Big Allegory Stuff played out on a relatively small stage. As the two major storylines collapse to a point in that episode ('New Canaan'), you get the sense that the story needs to stretch out, to fill the long Act Two, but the show's energy has all been invested in the mythology rather than the social texture. The simians in HBO's PR office got only one thing right when they claimed that the second season had effectively completed Daniel Knauf's story and the cancellation wasn't a terrible thing: the fact is, it was hard to see where the show was going to go from that point. And even the accelerated pace of Season Two didn't hold much promise.
Atop which, the show is tiring. Because so little happens, and the primary viewer involvement is wondering what it all means, Carnivale demands (even from those who've read episode guides and whatnot) total attention while never quite paying it off with narrative satisfactions. You can't watch the episodes end to end. (Compare the ease with which I sat through the final 14 riveting episodes of Lost's first season. I suspect you couldn't do the same with the second. Even The Sopranos in its later years has become resistant to such compressed viewing.) There has to be a balance between mere event and portent. JMS, creator of Babylon 5, knows this well - though B5 is more artfully constructed than written line-to-line, I'd say - the opening episodes are so trashy and clichéd it's shocking that the series went on to become a classic of its genre.
The other major weakness of the show is Nick Stahl's Ben Hawkins. He's simply too much of a cipher and too off-putting to make a good focus character. There's no richness to his outlook (compare Malcolm Reynolds, Joss Whedon's ethically daring creation on Firefly, a show that quite ably balanced one-offs and ongoing story arcs), so his reactions to the world aren't interesting, and his deeds are basically destined. Even a magnificent vision of the A-bomb in the Season Two premier doesn't awaken any insight in him. Pity. The 'false sun' that ushered magic out of the world (in Carnivale's mythology) was the most resonant creation on the show, and it would have been fascinating to see how that symbology played out.
In any case: Carnivale is worth looking at. It's not a bad show, just not a particularly engrossing one, with a weak protagonist, an overabundance (I never thought I'd be able to say that!) of mythology compared to small-scale plot, and a surprisingly denuded rendering of its historical setting. It might have amounted to something great, but it's tempting to see it just as a failed experiment, a risky effort to juggle the elements of fantasy storytelling and alter their proportions to a heretofore unseen degree. Let its fate be instructive to those who would tell stories in its extraordinary medium.