US and Israel had not war against Assad.
You just contradicted your first sentence.
Turkey could take over all Syria with ease if they provided aid to rebels in 2011-2012. There was no need in ground troops at all. Just send some cheap arms and maybe shoot down some barrel bombers.
But Erdogan watched still as Assad leveled to ground Syrian cities and villages (including 1 million Syrian Turks), as ISIS invited by Assad took over most of the border with Turkey. When Americans intervened to fight ISIS, the only force they could rely on were Kurds. Then Erdogan started to panic and initiated ground operations. He was forced to make deals with cheating Russians and made stupid S-400 deal.