Uh, I find Trump to be a scurrilous toad, but it seems to me that classified information is just one more bargaining chip that a president can choose to disclose or not in his or her discretion in performance of the office. Certainly there are times when disclosing classified information, even to an enemy, is in the country's interests.
In other words, if Trump did so as part of a strategic plan, he's entitled to do so as president.