The fundamental reason E3 has been failing for years is there just really isn’t a need for it in the general gaming population any more.
Nintendo have shown online works, Sony and MS are both in the process of following suit. That’s hardware pretty much gone, and software is perfect fodder for YouTube or Twitch.
the days when games mags gave away DVDs (heck, VHS tapes!) of the best footage shown at E3 because there was no other way to see it are long, long gone.
community events I can still see some sense in. But E3 was never really a community event, it was always a business/PR event. Sad as it is, I rather expect people will actually cope without it pretty well, and therefore it will never come back, at least not as it is/was.