It says beneath the video . .

"It appeared the Argentinian (President) wanted Trump to remain on the stage as they awaited other world leaders for an official members "family photograph"

Maybe that's why Macri appeared a bit miffed and disorientated by Trump leaving.

Such a "family photo" was eventually taken . . .



. . so Trump obviously came back on stage for that (presumably after he walked off)

Looking at them assembled for the group photo, seems to me to be a few uncomfortable gestures and expressions amongst the group, with the Saudi Prince, MbS, being (literally) way out on the edge of everyone else (far right in the group).