I remember this narrative being pushed here. There was definitely a fledgling group of people highly invested in the Switch failing. Obviously that narrative has basically disappeared as it became more and more obvious that Switch would be a huge success and potentially even outsell PS4.

That said, there was no way for people to know years ago that this gen would launch so bizarre, with very few next gen only games, and COVID delaying many things. On the flip side though, this has worked out for Switch owners, because rather than just get a lot of PS4/Xbone ports, it’s gotten unique and brand new games. Like the first two you listed, Rise and BD2.

Triangle Tactics looks amazing, can't wait. As long as Switch software continues to sell, the Switch will continue to get third party support.

Why would they do that when it is still selling well?

The Switch is seeing major support from indies and Japanese 3rd parties. For Western 3rd parties it's good, but it will die down once PS5 and Xbox Series are more readily available (probably starting next year). Indies and Japanese support will continue to be strong.

Of course 3rd party support wasn't going to die down immediately and anyone who thought that has no idea how new console generations start.
In fact the PS4 and Xbox One have more games announced/coming than the PS5 and Xbox Series. A lot of Japanese games are either going Switch only, or PS4 and Switch only.
To list a few games that are PS4/Xbox One with no PS5/Xbox Series version coming this year, Ninja Gaiden Collection, Mass Effect Collection, Neir Replicant, Samurai Warriors 5, etc.
Now a few Japanese games that have a PS4 version with no PS5, Saga Frontier Remastered, Legend of Mana, Akiba's Trip, Star Wars Republic Commando (not Japanese still an example), Disgaea 6, The Caligula Effect, etc.

Seeing these games not coming to PS5/Xbox Series, also the fact like 95%+ off all 9th generation games so far are also on 8th gen makes me think they should have delayed these systems. If it wasn't for backwards compatibility this launch would have been far worse.

I should have made myself clear. Indies totally count as 3rd party and they totally supported Switch since ever

When I wrote my first instance I was talking specifically about non-indie games, that was what I have in mind

Yes I don't understand why 2-old gen ports are counted like "support" when they were mostly outsourced ports who are released for the sake of getting some more coins. I understand support when a studio is actually including development time and effort and including a game in their already existing pipeline

What changed in 2020-2021? Well, we had official announcements for games like Rune Factory 5, Disgaea 6, Shin Megami Tensei V, No More Heroes 3, Genshin Impact, two Monster Hunter games, Crash Bandicoot 4, Plants vs Zombies, a new Lego Star Wars game, also the release of games like Ori 2, Immortal Fenyx Rising, Ninjala, Taiko no Tatsujin, Momotaro, Balan Underworld, Atelier Ryza 2, Persona 5 Strikes, Braverly Default 2, etc

Even if the development of many of those games started as early as 2018 they only become public years later. Meanwhile Sony and MS have studios developing games for PS5 and Series X/S even before they actually had both consoles officially confirmed, that's what support really means imo

Granted, we are talking about something that might be subjective. When I talked about 2020 I was stating my own perception. It was the moment that I realized that Switch 3rd party support was getting healthy and not restricted a very few games like Octopath Traveler or Dragon Quest XI

I think the Switch 2 will be out before those get released or at least 1 year after it released. 

What does that mean? Do people think the Switch Pro will get exclusive games and just forget about the 80million (soon to be 100 million)? 

Only if Nintendo changes to iterations instead of generations.  Following the NEW 3DS rules...

Like imagine there is a pro, so you have your high end model and the low end base model.  Both models will still get full 1st/2nd party support, but 3rd parties will be allowed to only port to the pro model of power is an issue (if the install base grows enough to support it mind you).

Then a few years later, release another upgrade (call it a pro 2).  The original Switch would then be phased out completely and the old Pro would become the new low end model.  The "Pro 2" would be the high end.

Then basically rinse and repeat till (if/when) the market no longer supports it.  Anything short of that and any upgrade will not abandon the base model at all without a full generational leap, as the install base is just too big.

But as more time passes, this is less and less likely as well.  At this point, I see no substantial upgrade till the Switch 2 in 2023-24.  If 3rd parties still support the base model with having some games with the Switch in mind (like Fenix Rising) and enhanced for the other consoles, or as 3rd party exclusive deals (like MH Rise, MH Stories 2, SMTV, Bravely 2, Resident Evil Outrage, etc) then the current model will have no problem making it that far regardless of what haters think.

Why would Nintendo release a switch 2 when sales are so great?

The same type of games that are coming to Switch now will still come to Switch OG.  But more demanding ports will only come to the pro.  Games that wouldn't have run well enough on Switch OG.  So Switch OG won't lose any support.