One of the characteristics of contemporary speech and writing is the constant irruption of bookishness (if not outright hyperurbanisms), by which is meant the substitution of bookish words and expressions even where traditional colloquial locutions would do.  This is the case of the ubiquitous present-day replacement of the word many by multiple (which, despite its dissyllabic written form, is phonetically trisyllabic).

Even taking into account the growing prevalence of linguistic hypertrophy in all purlieus of contemporary American English, trisyllabic multiple instead of dissyllabic many is to be accounted for by the irrefragable assault of bookish diction, which at bottom is actuated by a penchant for any linguistic token that would tend to signal the psychologically dominant valorization of written over spoken language as a matter of (imaginary) prestige in twenty-first-century American English usage.