Very interesting. This site has a fascinating 'behind the scenes' history.
Originally Diablo3.com was owned and managed by Mockery who, if I recall correctly, was based out of Quebec (maybe Ontario?). Umaro was aother primary admin for the site with him at the time (who was a bit more 'active' in the day-to-day running of the site).
Blizzard contacted Mockery about purchasing the Diablo3.com domain name in anticipation of the game announcement, but Mockery (I think, quite cleverly) opted instead to 'donate' the domain name to them in exchange for promotion - specifically, listing the new site (DiabloFans.com) on the official Diablo III website. When the game was announced, this led to a huge surge in users (IIRC from about 10,000 to 30,000 - practically over night). It was just before this 're-brand' that Umaro asked me onto the team to help with the graphical elements (e.g. new logo & banner, forum re-skin, etc).
Not long after, it was announced that Mockery was moving on from the site and selling to the Curse gaming network (I believe around 2010-2012). At first, the site experienced a lot of growth during this period as anticipation for Diablo III grew - however, I believe shortly after the game was released, the site's activity experienced a decline. My guess would be this was for a few reasons. I think the mutual anticipation of the game had held more energy than the actual game itself and, when it was released, I think a lot of the spirit subsided. Many of us were tired of the wait by this point. Additionally, some, like me, were probably disappointed in Diablo III and weren't as motivated to remain active in the community. These factors probably combined to produce a decline in activity.
Curse operated the site as part of its network for some time - before being acquired by Amazon / Twitch in 2016. Then, in 2018 the site (and many of Curse's assets, including DiabloFans.com and other similar sites) were bought by Wikia (aka Fandom). The current owner/operator of DFans is MagicFind - which appears to be a subsidiary of Fandom/Wikia - as their advertising is generated by Fandom (though I haven't actually confirmed that this is the relationship).
I'm guessing that the 'blackout' you've been referring to happened sometime in that 2018-2020 range (does that seem correct?)
ANYWAYS! All this has been very interesting to reflect on and research. I had to dig through some old emails from pre-2010 and do some Googling - which has all been surprisingly enjoyable. Thanks everyone for the nostalgia trip!