Could Usain Bolt have run the 2008 Olympic 100m even faster?

Yes, according to scientists who studied the race afterward, and even according to his own coach: Usain Bolt's famous 2008 Beijing 100m gold wasn't actually his fastest possible run, because he stopped racing before he finished it.

Bolt won that race in 9.69 seconds, a new world record and a crushing margin over the silver medalist, Richard Thompson, who crossed in 9.89 seconds. But Bolt visibly slowed down to celebrate before he even reached the line, his shoelace was untied, and the record still fell with no tailwind to help him. His coach, looking at how fast Bolt had covered the first 60 metres, calculated he could have finished in 9.52 seconds if he'd kept sprinting. Separately, astrophysicists at the University of Oslo analyzed his position, acceleration and speed against Thompson's and estimated a time of 9.55 seconds, give or take 0.04, had he run through the line instead of easing up.

Bolt himself didn't seem bothered by leaving time on the table. He said afterward that a world record hadn't even been his priority that day; he just wanted to win Jamaica's first gold medal of the 2008 Games, and he did. He went on to break his own 100m record the next year anyway, running 9.58 seconds in 2009, the biggest single jump in the record since electronic timing began. Between 2008 and 2016 he won the 100m and 200m at three straight Olympics, plus two 4x100m relay golds, and broke the 200m world record twice, taking it to 19.30 in 2008 and then 19.19 in 2009.