Their main business is Playstation 'at the moment'. Previously its their sole business. We went from 'Playstation only' to 'Playstation 1st'. The trend going on will lead to 'PC 1st' followed by 'PC only' after they stop making game console.
It will be continue being their main market. PC is a smaller market (in particular the AAA one) than consoles and they will only port there a few old games, it won't be their main market. Even if they would publish all their games and they would do it day one it would continue being a minor market for them.
There are zero reasons to think Sony would never go to a "PC first" strategy and obviously even less a "PC only" strategy. It doesn't make sense at all. The main revenue source for Sony is the 30% they get from publishing 3rd party games on their console, and they have zero reasons to change their strategy when they are breaking gaming history records on generating revenue, selling consoles and selling games for them. They are growing and the console market is growing, it would be really retarded to leave that to focus instead on a smaller market than the current one they dominate.
PC is the 3rd gaming market after mobile and consoles. Sony is only interested on it to get extra revenue source for their own games, that are becoming too expensive to make, and to get new fans to sell them consoles where they can play the new Sony games. Plus to grow in some countries where consoles aren't big and are focused instead on mobile and PC, so that they can't dominate with console alone.
A brand new console failing to sell more than an aging old console isn't normal, especially considering that Nintendo is practicing artificial scarcity.
100% of the consoles ever released have this sales curve: start with a few years with low sales (where PS5 and Series are right now), then they start growing until they are during a few years in a peak (Switch is at the end of this peak) and then their yearly sales start to go down year after year in their sunset tail (where PS4 and XBO are).
Some reach this peak later or sooner, some have a taller or wider peak, but all have this sales curve. So it's perfectly normal to have a console that is on its peak (Switch) to be selling more than consoles that recently debuted or are sunseting (PS and Xbox).
Artificial scarcity is a fanboy conspiracy theory concept that doesn't exist: Switch is available in the stores worldwide, if it doesn't sell more is because there isn't more demand.
The Japan Studio closure is a strong testament that they are surrendering Japan to Nintendo, mobile and PC, as they lick their wound. Maybe they will re attempt to reclaim the territory but it seems it will mean only 1 or 2 titles in the top selling chart at best. Nintendo games dominating the top selling chart from here on is the new norm in Japan, while PC continue to slay the digital market worldwide thanks to viral hits like Naraka or Phasmophobia, esports and others. At the same time, Sony's stressing over the ever increasing budget for their AAA games for their main audience on the next gen consoles. Their audience has forced them to implement an upgrade route for Horizon Forbidden West from PS4 to PS5. All the more reason they will have to port their games to PC
Japan Studio didn't close, they got restructured and changed their leadership. They will continue developing Japanese internal 1st party games under the Team Asobi leadership and they will continue publishing Japanese 2nd party games (like Death Stranding Director's Cut) but now their Japanese XDEV studio instead of being under Japan Studio will be under the global XDEV team. After restructuring, they are now hiring for both these teams, and for their Japanese 1st party team Polyphony Digital.
And are working to get more partnerships with Japanese studios (like the recent deal with Kadowaka) because in addition to bet on 1st and 2nd party, Sony invests hard on Japanese 3rd party excluives: almost every known Japanese 3rd party publisher and dev made at least one PS4 console exclusive. Jim Ryan said they PS5 will have more exclusives than any of their previous consoles, and since most of their excluives are 3rd party, it means they will have more than 3rd party exclusive than before. So it's fair to think they will continue betting hard on Japanese exclusives, as we seen with recent releases of people like Square or ARC System Works to name a few.
Sony game sales are between 70 and 80% digital sales, and their main markets are first Europe and second NA. This means the top 30 of physical games in Japan isn't something representative or meaningful of how are they performing selling games. Over 1600 million games have been sold until now for PS4 worldwide (and countring), versus over 600 for Switch. And because the best performing GaaS games like FIFA or GTA Online are on PS and not in Switch, or the biggest GaaS that are available on both like Fortnite have a bigger installbase on PS, there's also a ton of money more from DLC and microtransactions generated on PS vs on Switch.