Not defending Sony, but Microsoft has a lot advantages of their own. MS is already a massive company. So big that they make Sony look small by comparison. They also own and operate a state-of-the-art cloud platform in Azure. That’s not something Sony can compete with.
You also have to credit Sony for making the most of their first party studios and franchises. This is something Microsoft has really failed to do well over the last couple of generations, and probably contributes more to their number 3 position than anything else.
It’s cool to see the handheld PC market taking off, but MS needs to offer a purpose-built version of Windows for these devices. Without something more console-like that compete with DeckOS these devices are doomed to have a disjointed and janky experience.