The common definition of greed would be the selfish desire of more than one needs, the "little guy" by definition that us taken by investment scams or mass Crypto pump and dump scams usually isn't seeking more than they need, but in such a desperate and dire financial and economic position they are usually just attempting to gain some footing to put them on level ground. At the end of the day the scams exist because they work, whether you blame it on their the greed of the victim or it is just an act of desperation is irrelevant, the conduct that can and should be regulated is that of the scammers.

Greed is the desire to accumulate wealth for its own sake. I don't think it makes sense to characterize a low-income person as greedy for trying to improve their situation somewhat.