For decades, Temperance unions had a grip on American politics leading to numerous 'dry states' and eventually the 18th Amendment in 1919.
Where are they today? Most of them disappeared as the entire idea of prohibition was shown to be a failure and an enabler of criminal activity. As a political movement, it's long dead, it's adherents moved on to other things.
As a business franchise, selling buggy whips was stable for generations up until the popularity of the automobile. Oh sure, some people are still making and selling them but it's only a tiny subset of tack gear. Not something many would expect to make a substantial living at.
The same goes for gun control as a political endeavor and business opportunity. The CSGV tweeted a photo of "young leaders of the gun violence prevention movement". If they're there for an internship and experience, the only thing they're going to get is experience watching how an advocacy organization closes shop as their major players jump ship and the remaining staff figure out ways to keep the lights on. If they're there because they want to 'do something' about 'gun violence', the type of company they're keeping is mostly ignorant lunatics and frothing at the mouth fanatics as their public support continues to dwindle.
If they were smart, they'ld move on to greener fields. Of course if they were smart, they wouldn't be gun control advocates in the first place.