The problem is with considering the second path a backup path. It is a common problem with things that are considered to be a backup. In contrast, both paths should ideally have been in regular use. As a general policy, for resiliency, one should always exercise all of one's routes/suppliers/vendors, even if some are suboptimal, not just the primary one.

I completely agree. My comment is not to suggest there wasn't a problem or failure (clearly there was one!), but that we shouldn't assume incompetence versus conflicting priorities under limited resources.