I don't think "volunteered" is the right word to use here. Volunteering usually means you want to do the specific work because you believe in the cause and could even do it for free because it's important to you. These people were promised jobs, admission to universities, visa extensions etc to lure them in. Usually people who get trafficked don't have too many options in life, so they might have just thought it was a way to provide a future for themselves and their families. And we don't know what they'd been told said "help" would be. For all we know they might have been told they'd help with making sure captured Ukrainians were safe and treated well.
If you put out an ad soliciting for a domestic cleaner and then sent me to Gaza to "cleanse the land" I might be rightfully mad even if I knew you were an asshole.
It sounds like a couple of folks saw a lucrative job offer from a shady company and let their greed get the best of them... it's hard to judge them too poorly when Palantir and the NSA still find otherwise intelligent people to hire.