I would bet that 99+% of arrangements of 33 letters "look random" -- that is, there is no discernible pattern. Despite each arrangement having an equally tiny probability of occurring, if you randomly generate an arrangement, you're all but guaranteed to get something that looks random.

For aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa to appear, it is either an amazing coincidence, or there must be some non-random mechanism that creates it.