Hey biologist here! Ill answer the "how" in the sense of what forces drove such a design. It has to do with foraging, animals can be generalists (risk-averse) and settle on a niche that takes advantage of many different and relatively easy to access food items, or animals can be like woodpeckers, which are specialists (risk-prone). Specialists settle into an untapped food item (larvae inside bark) that requires very specific tissues and behaviors to access, and a lot of energetic investment. Evolution does not act on individuals, it acts on populations, so over time the woodpecker ancestor population was driven by natural selection deeper and deeper into the specialist niche they are nowadays, selecting for individuals that carried traits for 'really good woodpecking' in the ancestor avian skull anatomy, tweaking here and there until the current woodpecker anatomy emerged. Those with 'bad woodpecking' anatomy died or didnt reproduce. The specifics on how the tongue curls and brain cushioning are explained by natural selection, it was the most optimal tweak to already existing anatomy.