It was always going in time, tbh has little to do with leaks really as that has happened over the whole of my gaming life even back at ECTS many years past, the thing that killed E3 off is the expense for company's and the fact the internet video presentation allows them to control every aspect of it at a rock bottom price.
All these presentations of any kind even the game awards suck, they are out of touch cringe.
Still to me it really doesnt matter how the games are shown now or when they come out, it's rare that i actually get excited for anything these days as it's been done a million times before.
The key one I am excited for was the short trailer Sega made on there new batch of games, now 2 of them I am an ultra fan over so outside of that, GTA VI.
E3 was always going to die off and I highly suspect games com isnt far behind it, let alone others, there just isnt the need so much anymore.