A trial is a problem in maximizing the reasoning, under law and supported by fact, presented to a judge and / or jury. Those audiences have limited bandwidth to begin with. The "under law" constraint largely drives which reasonings and facts will be most important -- especially as all that must cross a barrier of evidentiary rules and trial procedure. The ability to weave all of that into a coherent narrative is crucial to communicating to the audience.
Boies can grab enough of the subject matter to speak to the key legal issues, and to ask experts the questions that define the boundaries around those questions. Another lawyer might know more of the subject matter, but that won't matter if they can't translate that extra knowledge into legal strategy.
Remember also that while you might be able to find legally pertinent technical responses to Boies' work in court, you're reacting to that after hearing his strategy. Good trial communication requires telling a unified narrative -- if your story doesn't already provide a basis for your response, that response will be weaker and may even distract from the story you do have. Boies' ability to anticipate arguments, mentioned by another comment, is crucial to all this -- it's not enough to have an answer, you really need to have that answer in advance of his question.