Gantz was never going to stop annexation, but his partnership with Netanyahu will now make it easier for the new government to move forward on it in a more effective way.
Gantz didn’t have the extra motivation to carry on the fight that Netanyahu does of using the prime minister's position to avoid a criminal trial and, very likely, a prison sentence.
Bringing the Palestinian dominated Joint List into a governing coalition would finally put an end to Netanyahu's reign but some Israeli MK's don't want anything to do with "the Arabs."