No one is going to give you a real answer, not sure if you're actually looking for one, but there is actually a fundamental reason for it.
In the UBS note, they said that 30% of DRAM is signed to LTAs slightly below today's price and that they expect 60-70% of DRAM to be on LTAs soon. If you didn't think this would happen, it's a pretty large development. In 2015/2018, LTAs were never signed. So now, MU, SK, Samsung, Sandisk etc. all went from "over earning but in a year or two will be earning signficantly less than today" to "oh shit, this might actually be able to earn close to this year's profits for the next 3-4 years".
Essentially, you're going from a normal cycle to supercycle not only in terms of price, but duration, or at least the market was pricing that in a lot more today than it was previously off the UBS note which is effectively making that more understood. That's also why the price target went to $1600 at UBS.
So, that's the real fundamental reason, doesn't mean that the cycle will necessarily go on until 2031 for example, but the market is pricing that outcome as more likely today than last week based off the analyst notes.