I too remember when these hit the tracks. Going from memory, I think that it was developed to decrease push in the corners and to decrease tire wear on the front tires because they share the load. During that era, bias-ply tires were what they raced with and they didn’t grip too well cold or hot. The front tires were about the same width as the two-wheel setup, but a lot smaller in diameter. So the tire patch on the track was almost twice as much as the usual setup.
The reality probably was a lot of extra weight with the added suspension and a lot of extra drag from the friction of the tires on the track and from the air flow above. I would imagine a lot to worry about on wheel alignment too. One was much more likely to have a flat or get a wheel knocked out of alignment.