The worsed part about Trump pulling out of Syria

People seem to be disagreeing on why it is bad that Trump is pulling out of Syria.

It is less about how it is bad that he steps out of Syria, but more how he stepped in and stepped out of Syria.

He stepped into Syria without permission of the Syrian government, supporting terroristic groups fighting against the government (including ISIS at the beginning), breaking international law. The war its self is even initiated by the Arab Spring supported by the CIA (and some supporters were very proud and open about it), and they turned every country against Syria as media coverage is dominated by them reporting about an alleged chemical attack that never happened (see reports from German ZDF and Russian RT-international on Douma Attack).

After fighting for a while, instead of securing the territory and dealing with ISIS they step out allowing Turkey to butcher their allies, and break international law again by attacking Syria.

The right way (morally) would have been stepping out of the country, asking Kurds to return to pre-war borders (that are outside Syria), handing over territory to Assad's troops, and lobbying for the acceptance of the nation of Kurdistan in the UN. The land the Kurdish are inhabiting is sparsely populated with 80% of Syria's oil resources. Since the world war annexing countries through war has become illegal, and this has become an axiom of peace. Turkey and Kurdistan shall be no exception.