We see two characters talking for 45 seconds. Then a bomb goes off, that was under the table. The audience didn't know there was a bomb: big surprise; but the dialogue between the characters is completely irrelevant and eclipsed by the explosion.
Now imagine the same scene, but before, we see a terrorist placing the bomb under the table. Now the scene is totally different, and every word that comes out of one of the characters' mouth is fascinating. Does either one of them know about the bomb? Will they find out in time? Will they survive? Etc.
Suspense > surprise.