The first thought was you would get two times the contact surface from four tires vs two tires. This seemed to work as the car won races before it's out lawed.
The second was with small front tires they could 'hide' behind the nose of the car, out of the air stream.
The fact that most other teams started looking at versions of the Six Wheeler as soon as it was raced makes one think it worked. F1 saw costs going out of sight and made the 'no more or less than 4 tires, no more than 2 in a single line' rule to stop the Six Wheelers.
And they looked really COOL!!!!! Thx