Both consoles have low supply due to stock, and because of that, they cant satisfy the demand. And since you cant satisfy the demand, you will have high demand for your product. (xsx,ps5)
If both consoles had high supply, everyone who wants the console will be able to get them. Because of how easy is to get the product, the demand would be low. (xss, switch)
The chip shortages is breaking the law of equilibrium. Which results in higher demand. Which is responsible for "Out of stock".
Until that chip shortage is fixed, both consoles will face this problem for a long time.
Xss has higher supply, which users here reported of its availability. Because of that, the XSS doesn't meet "higher demand" status, since supply exceeds demand. Same for switch. Switch has more supply, which makes the demand less, since you can buy one. XSX/PS5 have limited stock, which makes the demand for them higher. And because Sony and MS arent providing enough supply, both console will be in much higher demand. Its why its get "out of stock" status.
It doesnt have anything to do with n1 sales. Its whoever can satisfy the demand, will win that month.