Dunno what's surprising about this. It sold well in the brief window it was on Steam before it got Sweeney Swiped, and it only sold around 700k on EGS, which is a lot lower than I'd have expected this game to sell given the multiple extreme discounts it's had there (ie £7.49).
Only Borderlands 3 and WWZ, and to some degree Satisfactory have had good sales on EGS
https://playtracker.net/insight/posts/top-sellers-epic-store-2019
I don't think Epic's strategy of paying to get games pulled from Steam has been effective at all. They've obviously got a bunch of users registered from these exclusives and the free games, but they've not given people much in the way of reasons to use EGS over Steam for games that are available on both concurrently, and they've not even attempted to compete with Steam for functionality/features of the client.
Valve have spent over 15 years earning people's trust and loyalty. Epic have spent a year throwing money at the problem.