it seems to me that many of the superstar or once superstar online players, Polk, Dwan, etc made most of their money playing heads up with the exception of hitting it big in a mtt. It just seems like that is there is a greater probability of making an extraordinary amount of money playing heads up as opposed to anything else if you can master this type of game. Thoughts?
I agree with you 100%.
The big problem in a ring game (9 or 10 seater ) is that is that if you lose to an inferior player, there is no guarantee that your ex-money comes back to YOU at some stage. The guy that flukes a beat against you, could ATM it to everyone else except you. Or he donkee donks you with a beaut, gets up and says it's time to play punta banko. Wave your money goodbye ... Adios Muchachos
If you are plying heads up, your superior maths skills, patience, level of game understanding, card reading and situation reading helps you win. You are essentially locking yourself in the basement, with a bad player, until their money is gone. Just pass the food under the door

You need to have the right mentality for it though, because it is a fast intense game with no time to day dream...
If you look at a guy like Cy Jassinowsky (played for years under 'piejay') online. Look, he is far away from the money levels of Dwan etc, but he played 25/50 or 50/100 holdem heads up for years on ultimate bet. The guy was making bombs starting at a table with 10k , and up to 17k easily in a day (multiply by 3 tables).
All heads up !
He did get caught in UB superuser BS, but I think most players (at that level) got caught as well. You don't expect that a
poker site has someone using a superuser account to view hole cards.