As a Brit looking at this, my first reaction to the picture was "queueing?" - we never have to queue to vote here. Polling stations feel like they outnumber voters sometimes..
The law says that you have to have X number of machines per person in each district. It also says that noone should have to drive more than a specific distance to get to a polling place.
So the GOP drew the maps so that districts dip into very dense parts of the city, but then explode outwards for hundreds of miles. Now that district may have a thousand machines, but they are spread across thousands of square miles so that random farmers out in the middle of BFE have not just one, but multiple polling machines just to themselves, and all the inner city people have a choice of either standing in line for 2 hours to vote, or driving for 2 hours to get to one of those BFE polling stations and then driving 2 hours home.
Originally the idea was intended to provide and more equal representation.
In a dense urban setting, the different minority groups tend to cluster together but those clusters rarely follow any kind of orderly district lines. In a randomly divided district, the minority groups are often in contention, so usually won't vote for each other. This means that the the winner tends to be the white guy. If instead, you shape the district to follow the different clusters, then each minority group is much more likely to be able to vote one of their own into office. Unfortunately, the rules that were created to make things better for minorities were also able to be weaponized against them and eventually against the majority itself.