I, too, just read Tanenhaus' biography of Whittaker Chambers, and found it irresistible. Actually, the list of biographies I've read in the past six months is curiously similar to yours: Chambers, Custer (Son of the Morning Star, which I loved but which isn't really a biography), a bunch of books about Billy the Kid, and Nack's book on Secretariat (again). It's not surprising that we have a weakness for gunslingers, explorers, and true believers, given how different their lives are from our own.
As you say, Chambers' story is dramatic in a way that Morgan's is not--dramatic in an almost classic sense, I mean--because there is a kind of narrative arc to Chambers' life that satisfies us. Now, in general I think narrative is, well, bunk, or at least a dangerous conceit when applied to a life. But one of the things that made Chambers himself so compelling is that he clearly thought of himself as a character, and a character driven by an idea of who he was supposed to be. That idea changed, of course, from communism to Catholicism to anti-communism. But throughout Tanenhaus' book, you get this sense that Chambers is constantly imagining himself, and his life, as something to be crafted.
Along the same lines, James Miller's biography of Michel Foucault is a book I like a lot, precisely because Miller paints Foucault as constantly engaged in this project of imagining himself, of building his life as a work of art. (Chambers' ambitions were less aesthetic than religious, I think, but the projects are similar.)
With Morgan, by contrast, I never really got the sense that he was imagining himself. True, he sought out experiences that were different from those his father had had, and he knew he was J.P. Morgan, most feared man in the world. But in an odd way Morgan's life lacked the coherence of purpose--or perhaps just of narrative--that you see in Chambers or Foucault (or Secretariat, for that matter.) That probably sounds wrong, given the way everyone talked about him, and the self-enclosed intensity upon which everyone seemed to remark. But you can be really intense without being a great character in a dramatic sense. The irony is that we'd all probably rather live Morgan's life than Chambers'. Not because Morgan was rich but because he seems to have struck a nice balance between work, play, and love (all of my criticisms about his over-the-top Victorian romanticism notwithstanding).
In a way, this may be connected to what you're asking when you say, "What about Morgan was so special it led to his achievements?" You may not be able to find the Rosebud in Morgan's life because a Rosebud is something only dramatic characters--or someone like Chambers--have. There seems to have been no idée fixe that guided Morgan, not even Money or Control. In the end, I buy the idea that what he was really trying to do was hold things together and keep the economy growing.
In that sense, I agree with you that what Strouse has given us really is a bright, hard-working man who did what most other bright, hard-working men of his class would have done had they been put in charge of huge sums of money and given a well-respected name in international finance. Given the state of the national economy at the time, the broad consensus among the wealthy about the virtues of consolidation, and the economic pressures that were driving combination (in many industries, increased scale and scope did make firms more productive and profitable), it's not surprising that Morgan lent his energies to the merger and trust business. But this is precisely what makes me think that you maybe give Morgan--or perhaps Strouse--too much credit when you say that what was special about Morgan's achievements is "probably clear."
I don't want to keep flogging this horse--no, actually I do, since I keep bringing it up--but it's precisely the reasonableness of what Morgan did, especially in the sphere of business, that makes me question his reputation as a visionary and Strouse's reliance on the idea of "Morganization." To take the flip side of your counterfactual about what Morgan would have done if he lived today, had someone instead of Henry Ford started a car company in Dearborn Park in the early 1900s, I'm sure we would have had the assembly line, but I'm also sure that it would have arrived in a very different form, and probably unaccompanied by the $5 day and the idea of the automobile as something everyone would have. And I'd say the same thing about Milken and the junk bond, or Alfred Sloan and the decentralized corporation. But had someone else run the House of Morgan, I'd wager that he would have pushed through mergers and formed trusts and tried to stamp out competition. He might not have been able to step in as Morgan did and save the day in 1901 and 1907 and every other month, which is why Morgan's role in international finance does seem distinctive to me. But I don't think the course of economic history would have been drastically altered.
That is, of course, an insane conclusion. Louis Galambos and Joseph Pratt begin The Corporate Commonwealth, their history of the relationship between U.S. business and the state in the 20th century, with a section titled "J.P. Morgan's World." So, suggesting that Morgan was not somehow special is nuts. But there it is.
Ultimately, Morgan represents a dead end. He was a necessary way station on the road to a central bank and paper money, but his basic principles--the gold standard, private solutions to public problems, control of the economy in the hands of a very few people--all became quickly outmoded. (With the exception, I suppose, of his affection for large corporations. But even there Morgan favored trusts over actual mergers, and trusts quickly vanished too.) Morgan's authority depended upon an economic system in which there were very few individual shareholders (who had no real rights); public corporations were tightly controlled by the bankers that financed them; and the finance markets, instead of directing capital to entrepreneurs and fueling competition, tried to quell it at every turn. That's a system that Suharto would have found congenial. But it's not the system that we live in today. If Morgan's life as a financier has lessons for us, they're all lessons about what not to do.
In any case, thanks for talking with me this week. It's been a blast. Especially now that I know whom to call if I ever want to start a "Why Biographies Bore" club.