Without redoing their work or finding a way to have deep trust (which is possible, but uncommon at a bigcorp) it's hard enough to tell who is earnest and who is faking it (or buying their own baloney) when it comes to propositions like "investing in this piece of tech debt will pay off big time"
As a result, if managers tend to believe such plans, bad ideas drive out good and you end up investing in a tech debt proposal that just wastes time. Burned managers therefore cope by undervaluing any such proposals and preferring the crappy car that at least you know is crappy over the car that allegedly has a brand new 0 mile motor on it but you have no way of distinguishing from a car with a rolled back odometer. They take the locally optimal path because it's the best they can do.
It's taken me 15 years of working in the field and thinking about this to figure it out.
The only way out is an organization where everyone is trusted and competent and is worthy of trust, which again, hard to do at most random bigcorps.
This is my current theory anyway. It's sad, but I think it kind of makes sense.