How would Apple's policies be illegal? Epic entered a contractual agreement with Apple and then knowingly and intentionally broke it in order to benefit themselves.
Neither Apple nor Google is a monopoly in mobile games. By revenue Apple has about 60%. Check [1], search threshold to see what cases often require.
Taken together they would be, but then you cannot prosecute Apple and win without showing collusion between them and prosecute them both for collusion.
[1] https://www.justice.gov/atr/competition-and-monopoly-single-...