What did the astronauts fail to do which would have saved them from falling haphazardly through space?

They failed to prevent the rocket from exploding by failure to press the SCE(Signal Conditioning Equipment) switch.

Explanation:

In November 1969,Apollo 12 commander Pete Conrad with his crew members were on their way to the moon. This happened four months after men first set foot on the Moon. Due to the euphoria in the success of Apollo 11, NASA decided that Apollo 12’s mission should be more aspiring.

Pete Conrad was aiming for a precision touchdown but the rocket was hit by two lightning strikes which made him lose control of the rocket for a while and the space craft began falling till haphazardly till a crew member suggested the SCE switch should be pressed.

SCE stands for Signal Conditioning Equipment, the system that processed spacecraft sensor data for transmission to the ground.It was pressed after which they managed to steady it and later successfully landed on the moon.

no its not a run on sentence however i think you meant wet suits not sours also a run on sentence would be like surfers surf all winter long in southern california by using wet sours to keep them warm and the live their all year long