They care about exclusives, but just on their platforms. Which is Xbox and Windows, while Switch is supported sometimes because its not a direct competitor per se.

If they care about software sales and subscriptions then Halo Infinite must launch on X1 as well. Moving it to Scarlett only would only motivate hardware sales and would look bad for MS.

Mid Tier PC's blow the XBX out of the water. If someone considers themselves to be a gamer and game on PC regularly buying the newer games, their PC is better than a console's. That's pretty much a given. The XBX is literally considered an entry level gaming PC. It's equivalent to a dual core CPU and a GTX 1060, which is about $400 - $450. The PS5 and Xbox Scarlet I know will be equivalent to mid tier PCs.

Did Breath of the Wild launching on WiiU slow Switch sales?

Personally, I have no desire to see any more Halo or Forza games on Xbox One. From now on, I want them to be built for Scarlet, not ported to Scarlet from a console with inferior hardware.

And the vast majority of people that play games on steam etc have 'entry level' gaming PC's. 80% of steam users have quad core or lower. 

Only 15% of users have a 1070 or higher. Most have 1060, 1050 Ti and Raedon 5450 (10% have a 5450 and that's old as fuck). So yeah, being on PC means they might as well have the Xbox One version still. 

No. The next main Halo game has always been stated to be coming to Xbox One. Why change that now less than 2 years from launch?

Thankfully, Nintendo still gave older hardware owners their due with TP and BOTW being cross-gen. Microsoft should give Halo fans the same treatment. It probably would've made more sense for Halo Infinite to be a Scarlet exclusive, but not anymore.

And where did you get this information? Also Steam isn't the only PC platform.

No but steam has 90 million monthly active users. Which is the vast majority of PC gamers. And I doubt these numbers would be much different elsewhere.

I got these numbers from steam themselves from their hardware and software survery that they do of their users machines. 

https://store.steampowered.com/hwsurvey/Steam-Hardware-Software-Survey-Welcome-to-Steam

(Also correction on the 5450 part of my comment I mistook that for the 'other' section. But the point still stands, The vast majority of users have a 1060 or lower)

So you got this information from a survey, an optional survey. Where not everyone will participate. Where people can lie about their specs. The Steam survey does not represent every user on Steam. The survey also doesn't differentiate a PC "user" and a PC "gamer". Some of the most popular games on Steam or PC in general are really easy to run, so people who only play those games have no reason to upgrade. However, if you have a PC to mainly game on then it's pretty much a given that your PC will be more powerful than a console. This Steam survey thing that people bring up to make consoles look better has been debunked so many times.

But they also don't need to be... Most peoples PC's aren't sinking all their performance trying to chase 4k... Thus they can dial-up the visual settings at 1080P/1440P instead to have an overall better image than the Xbox One X despite having a weaker GPU in their PC's.
I would always choose Ultra settings at 1440P than Medium quality settings at 4k like most Xbox One X games.

In saying that...
I calculated that 32.54% of PC's on the Steam hardware statistics have superior GPU performance to the Xbox One X. - I only calculated nVidia GPU's, I didn't calculate PC's with multiple GPU's and I didn't calculate every GPU on the list... I got about half way which was enough to provide a rough idea.

https://store.steampowered.com/hwsurvey/videocard/
https://www.anandtech.com/bench/

Steam itself has 90~ million monthly active users.
https://www.pcgamer.com/au/steam-now-has-90-million-monthly-users/

Which using the power of percentages would equate to 29~ or more million monthly Steam users having a PC superior to the Xbox One X.
But like I said... It also doesn't matter, PC gamers get to choose to sacrifice some resolution to increase visual quality anyway even with specs that fall behind the Xbox One X.

How many Xbox One X consoles are on the market? A couple million? Yeah. There are more PC's with specs that surpass the Xbox One X.

It helps that the PC has vastly superior DRAM counts, faster storage, faster CPU's... Which means that the experience on PC tends to be a bit different than console.

The main selling point of the Xbox One X is that it has a semi-decent mid-range GPU (Although more low-end of the spectrum now that Navi and Turing are rolling out.)
But the games are still Xbox One games, they just look a bit prettier... And still a step behind what the PC offers.

A modern entry-level Quad-core CPU from Intel or AMD beats the absolute snot out of an 8-core Jaguar... Remember AMD's Jaguar was AMD's cheapest, slowest and nastiest CPU at a time when AMD's CPU's were cheap, slow and absolutely terrible, keep that in perspective. - Those 8-core Jaguars would offer less performance than a modern dual-core CPU. - Not to mention... Not all 8-cores of those Jaguar CPU's can be used for gaming anyway.

A Geforce 1060 can match the Xbox One X's GPU, but the kicker is... That GPU doesn't spend all it's resources chasing 3840x2160 resolutions, so it can output overall better visuals.

Steam hardware statistics aren't perfect either, there are many PC's with multiple-GPU's that aren't accounted for.