I planted h. Marilyn Inground, sandy amended soil. That was 5 years ago. They grew great foliage but never bloomed until they got moved to another location. Also inground, also amended, same amt of sun. They are magnificent this year but i don't understand the inaction of prev years. Any comments?

Possible the bulbs were not large enough to sustain blooms initially

They're certainly monsters now but I don't remember them being particularly puny.

It also takes them two years to make a bloom, so whatever you did two years ago did the trick.