Microsoft already has the XBox and despite being backed by one of the biggest tech companies in the world it's a rather weak product. To add to this, with every major studio acquisition they have done there has been a noticeable increase in game monetization and decrease in quality.

AWS has tried to get into the gaming market and only succeeded in creating giant money sinks even if some of their products were technically appealing.

Oracle making anything consumer-facing, much less something that isn't a total nightmare, seems inconceivable.

Valve is able to completely outmatch competitors in a chosen field because of what they are like as a company. No shareholders that expect quarterly growth. No massive bureaucratic corporate structure, just highly skilled engineers for the most part.