I feel TL lost because they stopped relying on Fenix
When your mid laner literally carried a whole game, you don't put him on a supportive role. You keep on giving him carry champions. Sure his off-meta picks were banned, but he still had Zed and Ahri to fall back on. They made him go Lulu twice on a protect Piglet strategy when Piglet was falling behind Sneaky. Quas was also doing quite well, and they didn't take advantage of that either. If they want to get third place, they should play off their strengths. Piglet has offered consistent play, which is extremely valuable in the LCS, but he has not proven himself to be the huge carry TL needs in clutch situations.
Tl;DR Fenix should have picked whatever champ he felt he could carry with, since he was on a roll. They had three games to play around to see what could work, instead of running a protect ADC comp for three straight games.