There is no way to "secure the network" from the endpoint. Any attack with sufficient volume to clog a hotel's pipes is going to create issues you can't mitigate post-arrival.
It's not like the hotel is sitting at a Tier 1 node with tons of throughput to spare. They are in the ballroom at the Crowne Plaza.
And I doubt any hotel you asked to modify their entire internet setup would acquiesce. You are confusing DDoS protection of a customer-facing website hosted with a DNS, with trying to mitigate an attack from the endpoint, at a hotel.
That's why you get a venue that has the capability for cross-connects and use GRE tunnels to route in-out traffic through a DDoS protect network. The network could have been setup to have zero points of failure, but the skimped on it and hoped for the best, and it didn't work out. A hotel has what, maybe T1 internet at best? I'm not sure how people running the event didn't envision something like this happening, but it was really poorly ran. From scheduling delays, to security and stability issues, this shouldn't be happening and it doesn't happen at well run events like E3 and EVO, sports streams, etc. It's a really amateur way to run things how they did, and people will take them about as serious as that.
And now the tournament director is threatening to sue the ISP for HIS incompetence? Lol that's so laughable. ISP's have EULA's and uptime agreements for a reason. That dude is just trying to save face and put blame on the ISP for his incompetence.