Too little info about what is happening behind the tug plane.
Seems like an early lift - off, low on speed, and he never levels off to build speed before starting the climb.
The actual accident is a stall, left wing drop, impact.
After an early lift-off, always level off to build best climb speed and only then start the climb out.
For some reason : The pilot is always pulling on the stick and never levels off to build-up to climb speed.
But? We don't know what was happening behind, so ??