Probably after all major studios pulled out. Turns out dumping tons of money on huge marketing shows that usually turn out a ton of drama probably isn't the best spend of money. It's much cheaper to run your own announcements under your own control. The better game show for fans would be PAX.
Not to mention there's the benefit to companies of being better able to manage the production of the announcements and avoid the random pitfalls that can happen at live shows. They can make sure the games they are announcing look their best and they can control their message. All three major console companies have had their versions of E3 failures that have led to major embarrassments for them in the past. They would rather not have that happen to them again if they can help it.
Not surprised, it feels like E3 has been on life-support for a while now. Still disappointed to know that it's over. Back in the day E3 was a highlight of the summer. Maybe it's just nostalgia talking but classic E3 was just so exciting. All these major announcements dropping at once combined with all the booths showing off new games. It was just great. I guess we have the Game Awards and Summer Games Fest as the big gaming events, but none of them feel quite like E3 use to.
E3 was great before communication became constant. E3 used to be one of the only times you'd be able to hear from the developers themselves, even if they were highly choreographed speeches and interviews we still got something.
Social media kind of took some of that magic away since we could hear from developers all the time. It took away their motivation to carefully craft messages and shows since they can now communicate with fans basically all the time.