At a basic level, the steps involved in setting up a fab are extremely serial in nature. While there are ways in which each step has been cost-cut in the past, amdahl's law itself limits it to a minimum of 2-3 years. If you want good yields and do it more properly, you will need 3-5 like GP said. And that is still being optimistic

Additionally, HBM requires 3+ times the capacity of DRAM, so it gets crowded out. They do command 5x margins, so the unit economics is ok. But this means that even new capacity will mostly be used to service HBM demand, and consumer or enterprise DRAM is unlikely to benefit at the same pace - it will benefit somewhat of course.