von Neumann was noted as being social and extraverted long before he began his lobbying and politicking, and was never described as a second Dirac, so I don't think he was simply acting out of expediency. If high intelligence enabled faking extraversion & social skills, which are useful in almost all contexts*, we would see a noted personality correlation with intelligence and increasing with intelligence, which we don't - extraversion is largely independent of IQ, it's Openness in the Big Five which correlates. High-functioning autistic people are also not noted for easily acquiring psychopath-level skills in imitating & manipulating without feeling.

* see for example the correlation of increasing extraversion with increasing lifetime income in the Terman semi-high IQ sample