It's likely that trump inadvertently revealed the classified information in the course of his incessant, ignorant bragging, horrifying the security officials present at the meeting.   Trump and his officials were then forced to try to come up with defenses when the story broke.   Unfortunately for them, as with other controversies, chaos ensued.   Characteristically, trump's massive ego prevents him from admitting he did anything wrong, preferring to resort to his usual bluster.   

The problem, going forward, is that other nations will think twice about sharing delicate information with our country, not knowing what trump might blab.