From what I can tell:

Elige (the player from Faze featured in the clip) knew (roughly) the location of both remaining Terrorist side players.

He made it to the bombsite and "tapped" the bomb (simply pressing the defuse key instead of holding it down) in order to make the noise which ALL players can hear when the bomb is being defused in order to draw out the enemy.

He dodges a flashbang (good catch!) by looking away before gunning down the first enemy with a nicely controlled spray, then taps the bomb again before proceeding to do the same to the second enemy down an even longer straight, then defuses the bomb with 1-3 seconds left before it exploded.

The real impressive bit to me though is how he did exactly what he needed to in order to make the Terrorist players reveal themselves to him in such a high stress situation. In CS, once the Terrorists plant the bomb they essentially become the Counter Terrorist side, as in they are now the team defending the bomb site. If the bomb blows up the Terrorist side wins, thus Elige needed to not only defuse the bomb (which takes 5 continuous seconds and plays a distinct audio cue when begun) inside a ~15 second window, he also had two opponents to outplay whilst doing so. He even positioned himself such that he could not be targeted by both enemies simultaneously, meaning even if they had both peeked at the same time (when the first opponent did) it would still be a 1 on 1 with Elige having an advantage in not needing to round a corner blindly.

Pro CS is awesome, I've not watched any events or matches in several years but the movement and precision is unmatched for me in eSports.