Learn to adjust.
-play a bit tighter during the earlier rounds.
-get your money in when you have any edge.
-most 'maniacs' are looking to double up or better or get knocked out. Its pretty common and the reason for it is because freerolls are long and tedious. You can play for hours and hours and make a minimal cash or nothing at all. So, you can either wait it out for all of the 'maniacs' to knock each other out, be a short stack by the time blinds hit 40/80-50/100 (usually) or risk it for an early double up or better, then wait it out. By the time 40/80-50/100 hits you're sitting on an average stack or better and play is slightly better at that point.
-Like someone said, they dont have anything to lose by playing like this. But they can gain a lot by taking risks. A player goes all in with 73o and is called by 4 players. They're either going to a) lose, but not risk anything or b) quadruple up and and be at the top with a big stack where they can wait out the early stage chaos and be at a better position to cash or win. So, its very little risk for a a big reward.