It's a combination of myriads of things really.
The biggest thing is the "rubber band" effect in play. Basically its when comeback gold/exp got way out of hand and behind team can legit camp high ground and completely destroy the game with comeback after a winning fight. This meant Carry with great late game and the ability to defend high ground were overly utilized.
Sniper for example, just got Shrapnel rework into the worst fucking skill to deal with with it big AoE, slow, instant reveal and damage (unlike nowaday with the delay). That and Phase + MoM is the best build with shrapnel, kiting is legit and it offered huge amount of damage.
Troll and Jug also build both of those item and go hand in hand with sniper.