How many years ago did they start construction on these projects? How many years before that did they greenlight the project? I'm quite skeptical the timelines are short enough to line up with the AI boom.
Micron is putting up over $100 billion for this expansion wave IIRC. You can't afford that unless you are certain the increase in demand is sustainable.
You want to assure investors that investment will pay off so you want to talk up your order book and market outlook.
You also want to take as much profit as you can now so if things turn against you it doesn't mean bankruptcy. A pile of cash fixes many problems :)