Do we have real evidence that AI bubble is real, or are people just speculating?

I feel like ever since 2008 nothing has ever really been the same and nobody really knows when it comes to the market. Yes, we have trends and plenty of data to try and make predictions but the market is just as volatile as ever.

What evidence do we have that AI could just be a bubble? 13% of GDP being Nvidia doesn’t matter if the circle of cash can continue indefinitely.