Regulators don't seem to have had anything to do with it.
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So what changed? Apple tells 9to5Mac that it has held further discussions with Epic. The result is that Apple has received proper commitment that Epic will play by the rules as legally defined.
“Following conversations with Epic, they have committed to follow the rules, including our DMA policies. As a result, Epic Sweden AB has been permitted to re-sign the developer agreement and accepted into the Apple Developer Program.”