Chip stock bubble

I keep hearing about the chip stock AI induced bubble.

Stock prices and market cap of these stocks have shot up quickly to the stratosphere, so I understand the bubble concern.

However, the valuation stocks like NVIDIA really doesn't seem outrageous based on earnings and predicted future earnings and the speed in which earnings are growing.

Question: Is because people believe these projected future earnings are way off? Or because demand will eventually dry up and the stocks come cratering back to reality? $NVIDIA(NVDA.US)$ $Advanced Micro Devices(AMD.US)$