Yes, hackers such as Anonymous thrive on 4chan, because they are given a forum that tolerates their criminal activities. 4chan should shut itself down, because it is a hotbed for hackers. But they do not want to shut it down because they make money off of it. But yes, 4chan is a forum for hackers to practice their craft.
Without a doubt, hackers like Anonymous don't thrive on websites like 4chan. They thrive on social media websites and hidden chatrooms where they plan hackings. They thrive while hacking websites, including banking and social media sites. With that in mind, hackers don't need 4chan in order to thrive these days.
While 4chan offers hackers a great place to come together and create their next big plan, they do not need 4chan to make it happen. Hackers can create and hack from anywhere and can come together on any site. 4chan is the go to place at the moment but after they are shut down or a new one comes along, hackers will move to the next one. Hackers will always be around regardless if 4chan is or not.
The thing with 4chan is that it's a public image forum where mostly normal people - and some slightly deranged kids - post funny pictures and jokes with each other. If there are any hackers, they communicate primarily through private channels, as revealing real illegal operations out in public would be an amateur's move. Perhaps some meet on 4chan, but that doesn't make it a den.
I do not think hackers thrive on networks such as 4chan. It is likely that some do look at the site and use to it their advantage but I also think that a lot of hackers are good enough to not really have to resort to thriving off of a website.