EA's first mistake was thinking that all "old-school gamers" want to play mobile games.
EA's second mistake was thinking that a series from the late 90s is the kind of game these "old-school gamers" with mobile phones would play.
EA's third mistake was using old, outdated mobile game mechanics few use anymore.
And the fourth and final mistake EA made was believing the Dungeon Keeper fandom would be alright with it.
And here's the reality:
"Old-school" gamers don't want old franchises on non-dedicated mobile devices. They want them on PCs, consoles, and dedicated handhelds.
America-wise, the mobile phone/tablet users that play F2P games with microtransactions are mostly "retro gamers" - People who went to arcades in the late 70s and early 80s because that's where the great games were, and became accommodated to paying in quarters in order to progress through a game they didn't own. Much of that generation of gamers didn't bother with consoles that much after the crash. When mobile phones became a critical asset, followed by the smartphone, "retro gamers" looking through the app store found games that are akin to the very ones they played in the arcades, with easy mechanics and controls, including the option to progress faster or easier through a small payment - It just feels natural to them given what they grew up with.
EA needed to aim for the attention of the "retro gamers" if they wanted it to somewhat work, but instead got the attention of the "old-school" gamers, used to the console and PC games starting from the mid-80s to early 2000s. They're not conditioned to making to small payments, instead buying the game straight up (or their parents did to be more accurate). Progression to them means having the skill - You can't pay your way through the games they grew up with. They want the whole game, not a base game with a bunch of it locked away though small payments. Getting the treatment "retro gamers" got back then feels like a betrayal to them.
In other words, EA should have watched and studied mobile phone and tablet demographics much, much more closely. There's a stronger divide in demographics between what they grew up with, where they lived, and what they played. EA got the completely wrong demographics' attention just by using a series they were fond of; a problem easily avoided through new IP.