The problem is that Bitchat is as vulnerable to this, as cellular service.

Many events have dedicated cell towers but even they cannot fit enough capacity in the RF spectrum, so they start dropping users.

Now, this gets worse with Bitchat. The 2.4GHz band is subject to way more interference from WiFi and a lot of other protocols. The band is also pretty narrow too.

To make it worse, Bluetooth only uses 3 channels for advertisements, which is only 3MHz of bandwidth, and is inherently worse due to being a shared medium with no central access control and coordination system.

Now consider a massive stadium. Open air means barely any attenuation. Tens of messages per second, each one rebroadcast by thousands of devices, all talking over each other, with so little bandwidth.

Congrats you have a distributed jammer.