Basically, they're investors who buy properties at wholesale prices, and flip them to other buyers (also typically investors) also at wholesale prices. This process is also called wholesaling. How they finance the transaction--whether they buy the properties with their own cash or assign them to other buyers in their buyers lists--is of no concern to a motivated seller. The only thing that really matters is if they can perform on or by the deadline.
Daisy chains typically result from newbie investors who haven't mastered the process of wholesaling. Everybody has to start somewhere, and everyone has made at least one mistake before. Many agents and sellers understandably would prefer to avoid any daisy chains, and sell directly to the investor/end-buyer. Yet, they fail to realize that many experienced investors prefer to qualify/screen their deals via the wholesalers. Stated another way, the wholesalers are the gatekeepers.
Yet, some investors opt to work with an agent to feed them leads. The key difference is that a wholesaler delivers deals gift-wrapped, ands/he has already run the numbers and comps. S/he has already set up escrow, so all the investor/end-buyer has to do is conduct his/her due diligence and close. Most agents are neither trained to run the numbers, nor interested in learning to run them.
On the other hand, some agents (especially ones who are also investors) either wholesale their own deals, or learned how to work with wholesalers. Either way, that agent will close more deals with investors.
BTW, some wholesalers might be willing to offer you 90% of your list price provided your list price doesn't exceed the current market value of your property.
This solution isn't for everyone. Many sellers want to receive top dollar for their properties, so they're really looking for retail buyers--not investors.