The wikipedia page covers it briefly: https://en.wikipedia.org/wiki/Phil_Katz
One of my favorite coffee shops is right near the PKWARE building off Pittsburgh Ave.
First, access - I can think of twelve bars within walking distance of my apartment, four of which are on the same block, and a total of eight of which are within two blocks of my apartment. Almost every grocery store has a liquor store as a part (not separate store, just separate section with a register), and some stores, like WalMart, sell booze in the normal aisles. It's everywhere.
Second, culture - in Wisconsin, if you're under 21 but a parent, guardian, or spouse then you are allowed to be served, possess, or consume alcohol, so teenagers drinking at home as part of a party is completely legal in the state. Bars are so close to the house, and every area has their own, so social drinking, especially when the winter is cold and dark (in parts of the state in parts of the winter, the sun is set by 4:30 in the afternoon), is very popular. Many of the locals, if they're religious, come from a history of Catholic, Lutheran, and similar religions that were typically not parts of the temperance movement, and many of the cultures that settled the land - Scandinavian and German most commonly - are also known for their relationship to alcohol.
Third, recent developments - the part of Milwaukee I'm in was decimated when the manufacturing base was systematically hollowed out in the late 1980s through the current day. Desperation and escape are two motivators to drink, and there are parts of the community that I'm in that have been hit hard by that.
Lewis Black has a bit about drinking in Wisconsin. It is exaggerated, but only slightly so, in a way that I didn't quite understand before I moved here: https://www.youtube.com/watch?v=7WlwumGkSec