Because major publishers noticed that to spend a shit ton of money in their own E3 and Gamescom conferences and booths isn't worth it, and was more profitable instead to focus their marketing budgets on online marketing like social media, releasing trailers in youtube and on making their own digital events on video, smaller but multiple of them per year.
Players wanted to have industry game showcases specially in Summer, and there was a void there that nobody wanted or knew how to do it successfully. Same goes with having a "Oscars of the videogames" awards, the industry wanted to have it but nobody did it.
Geoff had the contacts and did it.
Nah, they need to continue making around 4 general State of Plays per year (winter / very early in the year, spring / before the FY results report, summer / pre-E3, fall / pre-TGS) focused on showing stuff coming to PS mainly in the next 6-12 months, plus a couple game specific SoPs per year.