Why it took us so long to see a Bose-Einstein Condensation? Was it because we didn't have the experimental setup or something else?
1$\begingroup$ I would recommend you to read the relevant chapters in the book "Advances in Atomic Physics: An Overview" by Cohen-Tannoudji. He reviews the historical developments needed to achieve condensation in great details and addresses exactly your question, namely why it took so long. $\endgroup$– eranrechesJun 7, 2019 at 21:11
There is physics of condensation in superfluid helium, which was discovered in the early 20th century, but the interaction is so strong that it is not possible to describe the superfluid as a pure condensate ("quantum depletion"). So experimenters sought out to observe Bose-Einstein condensation in weakly-interacting systems like ultracold atomic gases, but that required the development of laser cooling (you need lasers at the right wavelengths) and evaporative cooling (you need good elastic scattering and high density) to increase the phase space density high enough to observe condensation.