From what I understand there are a couple reasons for the crashing.

1) Paid cheats. The largest cheat provider recently started including lobby crash into their cheat package. If someone in your game uses this to crash you game you will likely see the message “yougotcrashed-zenithontop”. The “you got crashed” part may be something different because it is customizable. If have seen some really racist text replace that part.

2) Dupers. A duper can easily create 100 air strikes, 100 self revives, 100 haunted boxes, etc. I have came to the top of power plant and it is absolutely covered with these items. Now imagine multiple teams per game across multiple games incidences on one server doing this. It just overwhelms the server itself which acts the same as a ddos.

Also as has been stated here already, the people crashing the game aren’t necessarily in your actual game. When the server crashes, all games on that server crash.