David E. Sanger in NYT on collapse:

'Rarely has a presidential decision resulted so immediately in what his own party leaders have described as disastrous consequences for American allies and interests. How this decision happened — springing from an “off-script moment” with President Recep Tayyip Erdogan of Turkey, in the generous description of a senior American diplomat — probably will be debated for years by historians, Middle East experts and conspiracy theorists.

But this much already is clear: Mr. Trump ignored months of warnings from his advisers about what calamities likely would ensue if he followed his instincts to pull back from Syria and abandon America’s longtime allies, the Kurds. He had no Plan B, other than to leave. The only surprise is how swiftly it all collapsed around the president and his depleted, inexperienced foreign policy team.'

Read the article here.

Sometimes it's just utter incompetence - other people see conspiracies. The conspiracy offers more comfort after all than the incompetence.