So, I'm a software developer and what knowledge I have of this is primarily due to just being a kid of a botanist who deeply cared about the subject, and spending lots and lots of time out growing food because we were poor and needed to eat. When your life depends on something, you learn as much as you can about it.

Breeding plants to be larger and consume more is probably a factor. Mistreating the soil is probably a bigger factor than people expect, though.

It's easy to think of soil as just a substrate, since we can't really see it or navigate it it's hard to properly visualise it. It consists of several strata, all with different properties. Healthy soil is full of bacteria, fungi, and little insects that live and die in it. All their activity help bring about nutrients and process the soil, aerate it. A lot of people are shocked to discover that the roots of plants also need air.

Industrial agriculture focuses a lot on big monocultures. As much as possible you want a field to have a single crop and nothing else. Herbicides are used to kill off anything that isn't the wanted crop, pesticides are used to kill off whatever might want to feast on the crop, fungicides... etc. Then we spread loads of nutrients over the field in the hope of replenishing whatever the crops drain from the soil.

It works to an extent. A lot of nutrients just run off into surrounding areas and waters, it's one of the reasons the Baltic Sea is basically dead.

Different plants have different properties. We mostly just see the top of plants, but like ice bergs a significant portion of them exists underground. Different plants have different root systems, some spread wide in the topsoil and help bind it together, preventing runoff and erosion. Some have really long roots (tap roots, like dandelion), reaching deep into the soil, pulling up minerals (nutrients) from the far reaches and eventually when they die, they get dispersed among the topsoil. Some fix nitrogen from the atmosphere, and bind it into the soil when they die and break down.

With big industrial monocultures, you lose all of that. There's nothing to hold the soil in place, there's nothing to pull nutrients across strata, there's no ecosystem to constantly process and enrich the soil for you.

The plants all evolved together, and just like animals they competed for different niches. Some animals eat vegetable matter on the ground, some evolved tall statures and long necks to reach further up. Some plants evolved wide root networks to absorb nutrients from a large area, some evolved long roots to penetrate deeper into the earth where other plants can't reach.

There's also fungi and bacteria everywhere, they live in the root systems, doing their work and helping the plants out, similarly to how we have bacteria in our guts.