What i dont understant is the certainty that both coins/forks are gonna live. If lets say 80% of all Hashingpower switch to the new Fork the old work will get stuck at a very high difficulty so transactions will take 100 minutes. This will cause more miners to switch until the fork is practically death/useless.

And i think if a fork will ever happen it will be made sure that at least 80% of the miners are behind this decision.