I think anyone is capable of grokking anything, just the time taken to do so is variable. people that give up on "learning" something (academia in your case) just don't want to spend that time.
p.s. I also gave up on academia for the same reasons :)
* Math is full of symbology with implied meaning. For example, theta is often used for 'angle'. How many other symbols have implied meaning like that? Granted, it forms dense, concise, precise papers. Which brings me to my second point.
* If you don't know the symbology, it's difficult to read it. I believe that people suffer reading comprehension problems if they don't know how to verbalize a symbol like 'θ'.
* Lastly, the symbols make it very difficult to google for concepts.