At least in Physics, on average every year there is more than one discovery that is worth a Nobel prize. So there is an increasing backlog of people who should get a Nobel prize. You can look at the list and check that people in the 1920s got their prize about 15 years after their work [1]. But recently people have been getting it about 30-40 years after.

[1] https://en.wikipedia.org/wiki/List_of_Nobel_laureates_in_Phy...