Phrase for advocacy group having a disincentive to achieve its stated goal?
Such a group is doing itself out of a job.
This is a set phrase, but I think do here means swindle:
5.3 British informal Swindle:
a thousand pounds for one set of photos—Jacqui had been done[ODO]
The group is so successful that it's swindling itself and will lose its own job.