It is known that the militants who had gone over to the side were part of the so-called “30 Division”, which the American military instructors prepared specially to counter the Syrian government army.
On Twitter, one of the members of the Al-Qaida group has the following entry:
A strong slap in the face of America (...) is a new group from the Thirtieth Division, which entered yesterday and transferred all its weapons to the Front of Al-Nusra after receiving guarantees for a safe corridor.
The term “new group” suggests that this is not the first transition of the “Syrian oppositionists” trained by the United States to the side of the “Dzhebhat an-Nusra” group operating in Syrian territory. And, given the specifics of the emergence of al-Qaida, it can be assumed that the American military instructors from the "opposition" initially set the task of moving under the banner of terrorist groups operating in Syria to overthrow the legitimate president and government.