Ok, then why are these mega corps not producing a net zero or net positive book?

At the debt levels they have, they need to start shoreing up their books or else the ramifications for the entire market will be apocalyptic

Because (some) investors with money still believe that this overspending (tbd.) on R&D is gonna pay off in the form of market share (or the generosity of our future AI overlords ;), and (some) dumb money is just following it.

An investment that needs to return 7x, alone, on hundreds of billions to trillions of investments... While not destroying the entire economy, or replacing it?

If you can capture a significant fraction of the gains made by automating lots of white-collar work, then those billions/trillions look more reasonable.

"Correct" investment volume towards early industrialization might have looked just as unreasonable without the benefit of hindsight.

How exactly is capturing 75% of white collar work not collapse western capitalism?