That was determined after an independent investigation by both the FAA and NTSB. This incident hasn't been investigated by anyone but Southwest Airlines.
> The captain opted to put the “newer” first officer in command on the short flight to Lihue despite the forecasts, according to the memo.
The less-experienced first officer “inadvertently” pushed forward on the control column, then cut the speed causing the airplane to descend. Soon after, a warning system sounded alarms the jet was getting too close to the surface and the captain ordered the first officer to increase thrust. The plane then “climbed aggressively” at 8,500 feet per minute, the memo said.
My apologies for asking the question when I could only read the first two paragraphs due to paywall. The archive link shared cleared up my concern, and makes it clear that it was human error during a weather-related re-approach. Thanks, though!