Denis put in a stunner of a semi final, played Rach preludes and brought the house down with them... if they did an 'audience award' as an extra, minor prize I think he might well have got that. Although also, the judging goes on their performance throughout the competiton, maybe Denis didn't pick the best overall programme. It was very romantic-biased, some of the others had a bit more genre variety overall.
Talking to the audience, all the serious technical pianists liked Sunwook or Andrew but all the 'ordinary' people who just appreciate their music liked Denis. I think his performance skills were the best even if his concerto wasn't quite up to Sunwook or Andrew technically. Which raises an interesting point, who to pitch your music at when you're at that kind of level? You're arguably a better musician if you can appeal to the serious audience, but you make a lot more money and play a lot more concerts if you can get the popular audience...