How many attendees were there? I tried to find some numbers real quick and couldn't manage to find them. For conferences (or any high density user environment), the density of users has a massive impact on how the network needs to be designed (omni vs. directional antennas, output power, individual channel selection, switching infrastructure, etc.). There reaches a point where the device density is so high that even narrow beam antennas at the lowest power setting can easily be hitting max associations. Really the only way to provide good coverage at any sort of event is to plan ahead (months in advance, especially for tech-heavy conferences) and not trust that the IT department of the venue will know how to properly set up the access.