What is beyond doubt is that the aircraft was in a low energy state when it hit the water. This is an extract from an incident report into a similar 737 incident in Australia
Had the aircraft encountered those conditions just before the go-around was initiated,the time taken for the crew to recognise and then react to the situation may have resulted in a more serious outcome. At that stage, the aircraft would have been at an altitude of about 200 feet, with the engines operating at a relatively low thrust setting,and with the landing gear and wing flaps in the landing configuration. Entry into a 3,300 ft/min downdraft at that point would have given the crew less than 5 seconds to execute the prescribed B737 windshear recovery manoeuvre to prevent collision with the ground.(ATSB 200100213)
Could be the Lion Air crew started their GA just a bit too late. The low energy state could have been the result of a high thrust setting reducing the sink rate to a survivable rate when it hit the water.