This is happening because the people in charge want it to happen. There are obvious reasons why this would be so. There's a lot of money to be made in selling out your country.
This is the most age- and sex-distorted "refugee" population cohort in history: not a single old person, not a single child, not a single woman; just young fit men from some of the most barbaric cultures on earth. By "barbaric", I mean countries where your ten-year-old's desirability as a Saturday-night date is perfectly normal, and doesn't require a corsage and a box of chocolates.