>The industrial revolution was enabled by more efficient agriculture feeing labour to do other work

you're not wrong, but that's not exactly what happened. Agriculture itself was mechanized by the industrial revolution, affordable tractors (tillers, farrowers, etc.) and harvesters. mechanized railroads put more perishable agricultural goods "closer" to urban areas, etc.

if you look at the growth industry before that, it was mercantilist overseas trade.

The flipside is that there must be other work to be done or people starve to death.

What is the next large labour-absorbing sector supposed to be?

What's the point of this comment? It's just a basic fact that everyone agrees with that wasn't put into contention by parent comment.