After the missed Golden got shot and Rockets rebound, one Golden fell down and the other was beyond the endline. (A Rocket was also beyond the endline)
So when Beard broke for halfcourt, it was a legit 4 on 3. Beard had momentum, could have pulled up and rocked a trey Or kept driving for a contested layup. Or looked to pass. Instead he chose the worst option, that being stop his momentum, step back and pick up his dribble. That gave time for both Curry and Thomson to trap him and allowed the fallen Golden player to catch up.
A timeout at 5.8? That would have been okay, but Beards killing all the momentum was the downfall.