In a piece on festschrifts for the LRB (subscriber only) - in this case for once left-leaning historians (or two of these) - Susan Pedersen notes they exemplify 'how through some opaque process of affiliation and acculturation, historians defending empiricist methods and resisting monocausal explanations float to the top of elite institutions' (32).*
Now, the process might not be completely opaque (irony is probably well-intended) as they initially seem to have gone to these institutions ('All did Dphils at Oxford') and, we could add, the obvious explanation of class politics. Complexity is for those who can afford and enjoy it, it speaks to a certain experience of that fraction, hence the plumpes denken ('crude thought') of 'monocausal explanation' (read 'Marxism'), seems so unutterably vulgar, yet so obvious to those who don't share that 'richness'.
Of course, the targeting of particular strategic moments (revolutions, popular dissent, etc.) by these 'complexifiers' indicates a precise awareness of the stakes involved, as does a 'practical materialism' about careers / academic power structures / institutions etc. Hence 'monocausalism' is both accepted as a truth and distantiated or diavowed precisely on the 'material' basis of class/social position.
* the sentence continues with this slightly snide, and typical, remark 'while those on less elevated perches stud their prose with the latest theoretical terms and pose and prophets of dissent.' There is something more to be written on the theorist as parvenu (to use Gilberto Perez's negative characterisation). Here the implication of posturing ('pose') seems to cut against academic ability and sincerity, staging theory, in Bourdieu style, as a power-game to seize academic reward. No doubt some do this, although I can't recommend 'high' theory as a tactic, but the pseudo-sociological explanation rests on that snobbery identified by Ranciere - don't get above your station, don't try any fancy (foreign) ides, you're on the make for coming from the 'wrong' class fraction... etc.