2. if the other coins that use LN have less fee and more tx/s onchain. then people will prefer to settle to those coins. especially if those coins are listen on the same exchanges and able to be used by the same merchant shopping cart tools
this is only true if bitcoin fees go up and stay up. for example if fees become at least $10 and stay like that forever then it is the end of bitcoin in my opinion. but the thing is fees have always gone up because of spam attacks not because of lack of capacity and that means they won't stay up forever so there is no point for anyone to go use an altcoin that is not even accepted anywhere to make payments they wanted to make with bitcoin.