I wish I had a solid source on this. The best I can find is a 6-year-old Reddit comment:

This particular jump with the BT-7 cavalry tank was performed by a tank test pilot Evgeniy Kulchitsky, he mentions in his memoirs that it was a very challenging test to perform (15m height, 42m length of the jump), requiring challenging practice and long preparation. You had to adjust the rotational speed of the tracks mid-air to not outright lose them, assume a (relatively) safe position and then continue to pilot the tank after landing to get it to the shore.

The reason for this testing was to make sure that similar jumps were a viable tactical option (fording rivers at speed, for example) and that both the crew and the tank could manage it and remain effective.