without reading the article: it's because every device connected to a cell halves the bandwidth available to each device, and after something like 30-40 devices the cell is full. so it hands over to another available cell, which may also be full. which means that if you're in a crowd of thousands, your phone desperately bounces off of every cell it can see and keeps getting rejected, boosting its signal every time to get farther away.
this is why we have mobile cell towers for events.