1. As you can imagine, not everyone has the wherewithal to launch a PE firm. Only people who are well connected in the financial world will get access to the funds. People who have friends in the investment sector for instance. There's plenty of stories about how VC (which isn't the same thing) investment is hard to get a meeting for if you don't know someone in the firm. PE works in a similar way, certain people know the players and get the deals together. Of course a lot of it is a promise of future business.
2. When a firm is acquired, the M&A advisors that did the deal get paid. When a firm is restructured (from bankruptcy), the same happens. Lawyers as well. These people all get paid to make the deals happen. Part of what happens is the M&A people will talk someone in the lending department into doing the deal. And remember it isn't just one bank or one lawyer or one lender on each deal. The lenders will all take a piece of the debt, which can be sold on (eg packaged in various tranched products) to investors (pension funds etc). If you smooth out the poop enough it doesn't smell so bad.
That's what I can glean from my far corner of the financial world, while I do work in finance I'm pretty removed from PE.