There are always unknown unknowns in trying new designs and/or materials. Even with all the simulations and calculations, nothing beats experience.

Sure, novel things should be tried, but in a conservative manner. Overdesign first, then optimize iteratively. Because failure costs lives.

I believe the failure happened in the joint between the wood and steel. The joint was a sandwich with very thin slices and with many nails. Anyone with materials intuition knows that puncturing a material to such a degree weakens it. Mix in constant moisture and single points of failure.. Should have been a couple of big old bolts and some bracings, alternately thicker slices in the sandwich

Glulam isn’t a new material, it’s over 100 years old.

How many 70 m span glulam road bridges have been built in those 100 years?

Yeah, exposing load bearing wood and glue to the elements requires some extra caution and engineering intuition