Like what happened to LTC to ETH.
LTC? That hasn't been GPU mineable for years. Its actually one of my first coins that I mined ever. I started mining it back in late 2013 when people were going crazy over bitcoin and crypto and I started mining it with my old Radeon 7850 (R9 270X) GPUs.
Profits were actually pretty crazy back then. I bought more second hand Radeon 7970 ( R9 280X) and I made at least $5/day/GPU for like 2-3 months or so. Then in Q2 2014 it started to get unprofitable but not as bad as it is today. One reason why it was unprofitable was due to LTC Scrypt ASICs.
They were released in 2014 and pretty much nothing for GPUs to mine until ETH was launched in late 2015. So ASIC pretty much killed GPUs back in 2014, just like ASICs killed GPU mining back in 2012.
Hardcore miner!
As you said the event. I think a big factor in the success of ETH is that a lot of GPU have no target at that time.