Did Pirelli blunder into brilliance?

The tires Pirelli supply F1 don't put down any rubber onto the track; they just wear off into tons of marbles, and they seem to wear to a certain point where all the grip just goes away, although there does not seem to be actual tire failure from big chunks of tread coming off worn tires. All that said, now that the teams have figured out how they work there is actual competition on the race track, something that has been sorely missing for years. From the way the bosses at Pirelli Tire acted at the earlier races do you think this was all on purpose or a happy accident?