Thanks to advanced genetic manipulation, by the 2030s biofuels could be grown as easily as weeds.
Every backyard could generate about one barrel of oil per year.
Instead of increasing consumption, this encouraged conservation and self reliance on a new scale.
Around 2035, cheap Chinese/Indian robot factory kits made it possible to build and maintain homes, businesses, and even vehicles using only local resources.
The unexpected final step was the invention of educational software that could actually make people smarter.
By 2050, the UN had almost a billion member countries.

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Probably the best hard SF novel ever written: Infinite Thunder by Jack Arcalon.
Buy the book
Read the chapters