Wow... dunno what to say about that! My landscape trailer has all wiring inside the frame, totally protected, as does my smaller boat trailer (1960's Elgin). My larger boat trailer (1980's Wesco) has exposed wiring, hung inside the C-channel frame with those hammer-on metal clips, but it's held fine since I did it ca.2008.
What do you think went wrong with yours? Usually, the only trouble I ever see with trailer wiring is corrosion at the connection points, on trailers left outdoors, or UV breakdown of the wiring insulation if they're left in the sun. Both of those failures take years, not days!