Not necessarily too short, formatting considered.  If Satoshi's paper had complete dissertation-style references, citations, and a lot more raw data in tables, figures, and proofs it could easily hit the 100+ page mark without adding a single extra word of narrative description. It would only need some minor restructuring to accommodate these additional elements.  Also, critical portions of the proof of concept client source code would be considered 'pages' in the overall paper length as well.  On a side note, for hard sciences, there almost isn't a separate dissertation writeup any more - instead I am seeing a trend toward taking 3 or 4 graduate level papers and/or articles you've already written and have them worked thematically into one dissertation since, for practical reasons, they typically share a lot the same research data you have already compiled. Satoshi's paper (if complete citations and references were added) would easily equate to one or two of these since it addresses multiple disciplines.