Ethonal eats unprotected metals in the fuel systems.
So metal lines. Metal parts in the pumps unprotected fuel injectors.
It also burns hotter so valves not designed to deal with that also tend to fail sooner.
There seems to be a lot of different answers depending on who you ask:
https://grassrootsmotorsports.com/articles/why-does-e85-run-cooler-and-make-more-power/