It's entirely possible the bubbles were manipulated sadly. Maybe that's a good thing though. Bitcoin needs time to grown and not just shoot up and down on a whim.
I don't understand why he would use an account to buy at a surplus rate and not use other accounts to sell at those rates. I.e. why not buy and sell from himself? That way he would not need to include fiat in the equation at all. Buying from his customers would mean having to produce fiat.
Well he needed the fiat coming in and it didn't matter about money going out because he blocked the withdrawls so no money went out eventually and that's how people lost pout because there was no real money or coins.
Why even go down that route? No fiat would come in by him buying bitcoins from exchange users. He was only putting himself in debt. It makes no sense. Unless he was trying to accumulate BTC?
It was easier for him to inflate the price by buying and selling to himself (using fake accounts) and then to sell the BTC at those inflated prices.
I think you are right we wont see another massive bubble. Just a slow grind.
If he was only letting fiat come in (stopped fiat withdrawls), and meanwhile sitting on a large stash of BTC, then the way to pay out least total fiat value of redemptions was a higher btc price ... meaning the show could carry on only until the BTC ran out, which would happen much quicker when the BTC price dropped. Sounds like it became just a classic Ponzi scheme by the end, robbing Peter to pay Paul.
Then you have to ask yourself if the willy bot was only source for the wave up why did the wave up end
before Gox blew up? ... there are other reasons that simplistic explanation doesn't stack up also, like Chinese exchange volumes and price reaction to bitstamp crash on way up etc.