How Did I Lose?

This is a serious question, I was completely and utterly baffled how I lost. Sometimes the game isn't very clear how you lost.

I had 11 units at level 9. All level 2 with one level 3. 6 Yordle, 3 Sorc, 2 Guardian, 2 Knight, 2 Phantom, 1 Ninja

(3) (2)

Veigar had Radadon and Luden's (these came from the Dragon and Rift Herald), Kennen had Red Buff, Cho had Morello Trist had Guinsoo, Dervish, and the disarm one. Leona had Frozen Heart, and Gnar had a giants belt. And I had 2 Force of Natures, I can't remember on who though.

Enemy had 6 units at level 6. 4 Level 3's and 2 level 2's. 4 Gunslinger, 2 knight.

(3) (2)

Trist had Dervish, disarm item, and Rapidfire. Lucian had Spear, Gunblade, and I think Bloodthirster. Gangplank had Shiv. Graves had the silence item.

I tried to position so that he couldn't get to my backline, but there wasn't much I could do about Tristana + Rapidfire. Towards the end, after my opponent realized there was nothing I could do they just put them in a straight line in the back...

I honestly believe I lost because Kayle is either bugged or ridiculously overpowered. Her attack speed is insane, I am not sure why she attacks so fast with no items. Not only does she have really high attack speed randomly, but her ult is up literally every other second on 2 people at a time. There was never a moment when 2 of my opponents units didn't have her ult on them. I tried to position so I was more likely to attack Kayle first but I couldn't seem to damage her faster than she got her ult up. Once she got her ult, I lost because then 2 people were immune for the rest of the battle.

but that my salty take on it. How did I lose? Is it because I built the wrong items? The game gave me a ton of Cho'gaths at the end I almost had level 3 Chogath before I lost, I think i was like 1 or 2 off. Should I have switched out Cho for more possible synergies?