Companies just because they have money doesn't mean they know what they are doing. And sometimes even less than random people.

Well, if half a million people are guessing on a choice of two options, some are going to get it right. But that's not due to the insight of the people, but due to numbers.

Every time someone makes the business argument all I can think of Microsoft flopping with Windows Phone despite all their money. Google failing with Stadia and losing opportunity they had with hangouts to imessage. LG bowing out of smartphones. Blackberry and Nokia too late to enter smartphones despite prior dominance. Epic was so late into trying their hand at digital distribution until 2018 when doing it earlier over the past decade would have made entry easier.

These examples really don't apply here.

• Windows Phone, Blackberry and Nokia were caught up in a massive market change where they where too little and too late.
• Stadia was a purpously risky gamble to be first at a potential "next big thing" and was scrapped when the global economy crumbled and cloud gaming showed no signs of wide spread adoption. If anything, this is the opposite situation than Epic and Linux.
• Hangouts was renamed and merged with other Google chat apps, but in the end they now have messages, which is the messenger with the highest install count worldwide.
• EGS is still a comparably new thing, considering that Steam is in the market since ~20 years while the EGS is here only ~5 years. They are growing steadily, so this is not an example that we can look at in retrospect, because it's still unfolding. Also, sure it would have been great if they would have had to run a game distribution platform in 2003, but their money shower didn't start until Fortnite exploded in 2017. And they pretty much immediately got into the business when they had the money to.

Also, there are some other factors in play that you didn't consider.

Smartphones exploded between 2007 and 2010. It went from nothing to almost everything in just a few years, and those who got lucky and where ready at the right time managed to take the new market. Windows Mobile proves that it's not enough to be super early. You need the right timing in both directions.

There is no indication that Linux will have >50% market share among gamers within the next 3 years. Yes, it nudged Linux over the 3% mark but at that rate it's going to take a long while. Also, contrary to smartphones vs feature phones, the steam deck is an additional gaming PC for on the go. It doesn't replace desktop gaming.

Also, when it comes to mobile gaming, the Steam Deck is a distant fourth between Android, iOS and the Switch.

And even if you limit the scope to x86 mobile gaming, they are by far not the only competitor. There are lots of others, many of them using Windows, who do the same.

And the biggest edge the Steam Deck is it's value, because Steam subsidizes the Deck with their Store sales. Most people don't care whether it runs Linux or not.