The only reason I can think is that some managers are paid daily/weekly with real btc/eth and if this is true there is no point for them to report a scam even if they find it since they will get money anyway.
NOTE: This is a personal supposition, I don't know how they are paid.
Having been in charge of a few campaigns, and having talked with the "managers" that are involved in the cases cited here, I have to say, this is wrong, at least for those incidents I am aware of.
Managers usually get paid once they complete their work (which is either at the end of a round when a payment is made, or at the complete end of the campaign). Neither of the managers in these cases saw any money.
ughh123 themselves admitted that they have been scammed (not paid for their managing) in not only the TQ campaign, but also at least two campaigns before that.
The way I see it is that a lot of super inexperienced people are looking to find their way into management positions, without really knowing what it means, what they should be doing, and what the risks are.
By making theses steps, they do not only take an uncalculated risk themselves, they also put others at risk (the people joining the bounty, trusting the manager).
And I'm not saying that new people shouldn't start managing campaigns, we all have been inexperienced at some point. But they should take more time to educate themselves and research, before they take onto positions.
Although one example of a situation like the one described in your post comes to mind, the
aTriz incident.
I would however hope this is an exception and not all managers are acting like this.