Decided to try out Cake Poker

So I downloaded Cake Poker today. I was curious so I decided to do it. I quickly entered a freeroll to win a $40 seat into a freeoll into millions $250K semi-final. I was playing really well. They were 2817 people entered. I didn't start checking my place into it got under 100. My place was ranging from 15th-20th, the top 20 win a ticket. Got down to under 40 and I'm still in the top 20. Then the hand that crushed me. I make a set and the other guy decides to chase a flush and hits it on the river. I didn't go broke but I was short stacked. Luckily I just called his re-raise on the river. I don't understand players doing that. He doesn't make the flush, he's crippled. He was in the top 20 at the time as well. Doesn't make much sense to me to chase like that so close to the cutoff. I wasn't too happy but hey, that's poker.