I agree. I know why humans must diversify, to avoid having all their eggs in one basket, but why is it obvious that companies should? Their owners should invest

I agree. I know why humans must diversify, to avoid having all their eggs in one basket, but why is it obvious that companies should? Their owners should invest in other things, but maybe it's better to admit that a given company is a bet on a particular niche, and if it dies, it dies. In fact I'd go a bit further, and say that if every company seems to become a conglomerate, that's a sign that something is broken in how a country works. If it's advantageous for two companies doing completely different things to be under one name, one roof, then it's likely that their real skill is in something else, like political connections, not in making whatever products it is they make. And that's unhealthy.