In the early days of the information revolution, when computers were new and being nerdy was still seen (almost universally) as a bad thing, a very high proportion of computer enthusiasts were people already on the fringes of society, for one reason or another. For a large number of them, hacking was a way to express their preexisting antiestablishment tendencies. For a lot of them, they were also your basic angsty adolescents and young adults rebelling against The Man as soon as they found any way to do so.

As time went on, computers became more mainstream, and lots more people started using them as part of daily life. This didn't mean that the number of antiestablishment computer users or hackers went down—just that they were no longer nearly so high a percentage of the total number of computer users.

So the answer to "what happened to all the hackers fighting for personal freedom and privacy?" is kinda threefold:

1) They never went away. They're still here, at places like the EFF, fighting for our personal freedom and privacy. They're just much less noticeable in a world where everyone uses computers...and where many more of the prominent institutions actually know how to secure their networks.

2) They grew up. Captain Crunch, the famous phreaker, is 82 this year. Steve Wozniak is 74. And while, sure, some people reach that age and still maintain not merely a philosophy, but a practice, of activism, it's much harder to keep up, and even many of those whose principles do not change will shift to methods that stay more within the system (eg, supporting privacy legislation, or even running for office themselves).

3) They went to jail, were "scared straight", or died. The most prominent example of this group is, of course, Aaron Swartz, but many hacktivists will have had run-ins with the law, and of those many of them will have turned their back on the lifestyle to save themselves (even Captain Crunch was arrested and cooperated with the FBI).