2 Brawler with no Knight bonus doesn't beat Void (True Damage) Especially when boosted by Sorcerer damage ( at least 3 Sorcs based on their team, or a 40% damage boost to all skills). He also had (3 Yordle for 30% Dodge), and Kindred for invuln. You had no such invuln.
Second had Knights + Guardians for a LOT of Armor, and an itemized Vayne/Draven to poke from behind the defense.
I would have sold the Garen and got another Brawler..... like Vi so you could have (2) Hextech
Item's also could have played a major role in why you lost and they won. Due to the nature of the TFT end game screen it's hard to tell that kind of thing.
I don't wanna feel like the rest of the fanbase, but your composition really sucked. The only reason you got up there it's probably you put good items on strong units (jinx, yasuo, draven), and maybe the 2nd did the same but better. He had a horrible comp too, so it was close between the two of you. The 1st was actualy a whole different level, and his composition wasn't perfect at all, but all those lv3 and stronger synergies (yordles, voids and sorcerers with good champions) made everything
Yeah, the Garen was a wasted slot since you didn't even have 3 Nobles or 2 Knights out. That's probably the biggest disadvantage. Never have a 1-cost unit out that late if they don't have any synergy.