Why does the mexican government allow them to stay?

Why is Trump even allowing these fakers the ability to file Asylum Claims?

Why are the Border Agents approving the initial 'Credible Fear Test' and allowing these people
into the U.S. to proceed with a court hearing?

Sessions changed the Burden of Proof onto the migrant requiring verifiable evidence of there 'Creditable Fear'
and absent that verifiable evidence, the agents were ordered by the DOJ to deny entry at the front gate.