Epic never expected to make money on exclusives. They were using them as a loss-leader to force people to use their shitty store. Fortunately it looks like they've lost enough money to make them stop or at least cut back on their shenanigans.
This has been the case with console addons all the way back to R.O.B. the Robot, if not earlier. People won't buy an addon if there are no games for it. Companies won't make games for an addon if no one buys it. Catch-22.