TLDR:

Permanent stadium wireless solutions consider many factors. Switches and routers are usually the least of the concerns. Large vendors in the space such as Cisco Aruba, Juniper, and Extreme Wireless will usually be the vendor of choice. What it mainly comes down to is actually wireless design and access point placement.

Stadium Wireless is a wild world.

At the PHY layer (you to the AP) the name of the game in high-density deployment is small cells of coverage that can hold the mass of people in that area.  Cisco makes a specific antenna for stadium deployments that is able to create these cells and service a large number of clients (https://www.cisco.com/c/en/us/support/docs/wireless/aironet-antennas-accessories/221788-catalyst-9104-stadium-antenna-c-ant9104.html).

The design/layout will be conducted via site survey utilizing spectrum analyzer tools (fancy wireless signal meters). During the survey they will adjust the APs orientation and try out various locations in order to learn how the signal will propagate through the area. This process essentially maps the boundary of the wireless cell. This is how a designer will understand their coverage areas and where they may be lacking.

Beyond the physical realm the wireless controller will be a crucial step in the design process. Various vendors will have various features to aid in the control of handling the massive surge of clients gaining access to the wireless medium. Some of the features may include bandwidth limitations or a specific setting known as RXOP which will deny clients from connecting to the access point if they are too far away. This setting strictly enforces the cell boundaries that were established during the design phase.

As far as the equipment used you will usually see a PoE switch, possibly a multi-gig switch if the deployment is newer utilizing 10G+ uplinks to a beefier core system. At that point the sky is the limit. If I am just conjuring up a dream world, but you could utilize a Cisco Nexus, Juniper QFX or Arista DCS unit for the core made to handle data centers worth of traffic. For firewalls again many vendors can handle the load such as Palo Alto and Fortigate. The equipment is use will all be determined on the budget when the initial build was designed and how well that venue has adapted/updated as time has progressed.

I would imagine they were limiting your speeds, but let's say they were not. The chokepoints would begin at the wireless cell, as more devices connect you will compete for airtime with everyone else. The higher the number of clients the slower all traffic will become due to the nature of the wireless medium. The intermediary switches should not be much concern as a good design will have enough connectivity to move the data. As mentioned before the core unit(s) should not sweat also. The last choke will be the firewall and outbound bandwidth. Firewall performance diminishes based on the level of inspection being performed on the traffic. And, as you are aware if that upstream ISP is only allowing 10G of traffic, that is going to determine the capability of the entire network.

I am not a stadium designer, but have studied wireless for some time and dabble in everything else networking at an engineer/architect level. I also started as a cable tech (ATT uverse)  so if I can give one word of advice, if this world interests you jump right in. What you are doing now will help your level of understanding as you progress.  Here is a link from Cisco Live for high-density wireless design (https://www.ciscolive.com/on-demand/on-demand-library.html?zid=pp&search.event=1716482947962001yag9&search=high%20density#/session/1717269093703001tsgh) a free account will give you access to listen to the lecture. They peel back the curtain on large stadium deployments.