This is a big generalization. Not everyone is looking to automate tasks, so it's not a sign of mismanagement that someone has employed a novel way to reduce work. Efficiency is a goal of management, but not the only one. It's unrealistic to expect a company to pursue and capture every inefficiency. Often it's cheaper to allow aspect of "work" go unabated than to invest in both the feasibility and implementation of its automation.

If you're referring to mismanagement due to knowing what an employee is doing, I think that too is a generalization. Dovetailing with the above, if someone is getting a job done, why invest time and resources into auditing how that's done? In 99% of cases that's waste.

In the grand scheme of things, big companies are vulnerable to degrees of malice and abuse by their employees (not necessarily ascribing those terms to these actions). But they don't necessarily fail to exist because those vulnerabilities were used.

I think you underestimate how defensible some businesses are. For example, a supermarket or bank in Australia. “A matter of time” could be your entire career.

Yes. I worked for a company that has such a moat surrounding its line of products, it will a couple of decades to erode. 70% of the people there were doing very little on a day-to-day.