Yes, we can see how Big Tech and Apple's huge margins get compressed all the time, they never expand. They are going to zero soon it seems :(
You can't say that in general because it also depends on the moat.
Apple has 75% profitshare in the smartphone market not because they have the best smartphone but because they sell iOS. This is why Apple can charge much higher margins on iPhones then any other smartphone competitor. Competitors use Android and are basically exchangable so their HW is commodity more or less and margins are much lower.
The same will happen with Nvidia. Nvidia will offer complete data center solutions and many other SW/HW solutions for AI and accelerated computing and will charge high margins for that. HW sellers like AMD will sell only chips which will compete with commodity ASICs.