The SHA256 hash algorithm produces what looks exactly like a random number in the range 0 to 2256-1 (1.1579208923731619542357098500869e+77). Each of those values should be equally likely.
So if you produce a large number of these by altering the data to be hashed, you cannot steer the results and most of the results will be a large number.
Some of the results will be a small number and a few will be very small. It is perfectly possible that the first result that is small is also very small - there is nothing impossible or surprising about that.
Since the genesis block had no history, there should be no expectation that the target value was especially precisely calculated to match the exact hashing power available.
Furthermore, I would expect the target would have been high (low difficulty) since there were very few miners (only one?) - The higher the target, the more space there is for a solution to be some orders of magnitude smaller than necessary. If conversely the difficulty was so high that hashes had to be less than 42, there would be no room for a successful hash to be two orders of magnitude smaller than needed.