They definitely had more 3rd parties on their stage last year thanks to Sony skipping E3, I think they had 10+ AA and AAA 3rd parties at their conference, including Elden Ring, Cyberpunk, Borderlands 3, and Dying Light 2. As for 1st and 2nd parties, last year there wasn't a ton they could do to take advantage of Sony's absence, many of their new 1st party studios were only recently acquired with the games they're developing not far enough along to announce at that time, and there wasn't alot of point in them making a ton of 2nd party deals for XB1 when this generation was already a lost cause for them. Their next-gen hardware wasn't far enough along in development for a full reveal yet. They did the best they could considering it was the last current gen focused E3.

This year though alot of that that is not a big problem for them. They can show off more of their hardware, including the rumored Series S, if they chose to. They can acquire more studios and announce them. They can announce most of their Holiday 2020-Holiday 2021 1st/2nd party lineup, and maybe even tease some 2022 games since their next-gen console is unveiled now. Many of their new studios like Playground's RPG studio and The Initiative have games that are far enough along to announce now, at the very least in teaser form, quite possibly even with in-engine trailers or gameplay demos. As for 3rd parties, I'm sure there are plenty who have been waiting on PS5/XSX announces to announce their next-gen games, and if they want to announce those games at E3 in order to take advantage of the large streaming viewership numbers at E3, the MS conference is pretty much the only conference for the publishers who don't do their own conferences to announce those games. EA, Ubi, Bethesda, and possibly Square will announce their games at their own conferences again, but that leaves Take-Two/2K, Activision, Warner Bros, Capcom, Namco Bandai, Tecmo Koei, Sega and more as possibilities who might be looking at Microsoft's E3 conference to announce any next-gen games that are far enough along to be announced now. There is alot that they can do to take advantage of Sony's absence, if they chose to. 

Fine by me, Sony didn't attend last year and it didn't hurt them. During this generation they've shown that their own events get enough attention, with the unveiling of the PS4 and the PS4 Pro, there are many other events to attend too. When they reveal the PS5, no matter where it is, people are going to know. Just look at how people are getting hyped at the idea of a February event. The truth is that Microsoft don't need E3 either, it may still be a huge event but it isn't as necessary as it used to be.

Sony has plenty of other events as well as their own throughout the year.

So explain to us why Sony not being there for E3 will potentially screw up their holiday period launch.

None of the big 3 launched a console last year either.  Timing matters.

(referring to bold)  That is not necessarily true.  E3 is an event.  People take special time out to watch an event.  If 1/3 of the Oscar awards broke off and did their own thing another month out of the year, then it would get a lot less attention.  Oscars get a lot of attention just because it is an event: lots of celebrities in one place, people like to see what they are wearing, people want to see the best jokes and Oscar highlights, etc....

E3 is the same way.  Lots of games are shown off at E3.  Lots of developers are there to talk about their games.  Many youtubers make special videos about going to E3 and such.  It is an event!  People pay more attention, because it is the biggest gaming event of the year, by far.  It is really dumb for one of the big 3 to just skip the biggest gaming event of the year, especially a year when they are launching a new console.

So you are saying Sony has no respect because they ditch dying show for their own shows around the globe?

In the last thread I said there was no way in hell Sony would skip E3 this year. I was wrong.

Even the year when Nintendo only had BOTW they still attended. Because at the end its quality > Quanitity

Was it 2018 where they tried something different where the audience moved to different venues? But the audience POV was pretty wack. 

Nintendo also does the Treehouse live stream for in game footage. And recently they do esport/competition events too (like previously they did Smash, Splatoon, Super Mario Maker and the Nintendo World Championship) 

Maybe respect to the NA fans?