Not 'rigged' per se, nor impossible. Breaking it down, you'd have (My numbers are under the assumption that every team has equal chance, which is not accurate. There would be no hard number to put for individual teams chances though, so making it even between them is the best way to go for this argument):
1 in 4 chance on every first seed for groups, or 1 in 258 for all four top seeds. Same for second seed (since you can't determine who is first seed beforehand with this argument, you have to count all four teams still), meaning perfect guesses in groups are 1 in 65,536 chance.
Now, counting Knockout separate to start out, you have a 1 in 2 chance for any single team to make it to semifinals, so 1 in 16. (Again, this is not even considering who the teams are, or how good they look. This is simply flat chances for all teams for the sake of argument only.) Semifinals are 1 in 4 chance, making it 1 in 64 so far. Finals adds the last bit, putting us at 1 in 128 for Knockouts - a much less daunting number.
To finish off the argument, we just combine the two, giving us a 1 in 8,388,608 chance for a perfect draft. So... you are actually more likely to draft correctly - even without paying any attention - than winning the lottery.
Of course, with sports, even eSports, you have estimated odds for each individual team, making this number higher or lower depending on who you pick - in theory. Remember, they are always ESTIMATED odds. Odds don't decide winners. Winners decide winners.
I know this might seem unneeded, but I more just wanted to point out, yes, it is possible. Just very, very unlikely. lol Still, I'd rather take my chances on this than the lottery. It is almost twice as unlikely to win the lottery (closer to 1.6 times from what I'm calculating.)