For one they didn't scale properly, they got huge and failed to empower the moderators with the right tools to run their subreddits. Second they kept too little control of the site and it descended into mob rule rather quickly, this forced the formation of factions and the related struggles that continue to tear apart the website.
Also terrible transparency on the admins part, although I think the mods had enough power and some took it a little far. Large subs needed something else because 20 something people controlling 3 million doesn't work well on the internet. Also, are you the same Laurelai?
Yes I am and the mods on reddit in the defaults for the most part are absolutely terrified of being witch hunted by the userbase. The mods did not have the ability to detect or ban alt accounts or lock threads or hard delete anything, not even doxxing. Other forums have figured all this stuff out and reddit wont budge on it. The crowds are so easily swayed and manipulated into grabbing the torches and pitchforks over the most absurd stuff.
I think reddit would have really benefited from IP bans.