Alma 42:10

therefore as they had become carnal, sensual and devilish, by nature, this probationary state became a state for them to prepare: it became a preparatory state.

People had become worldly, selfish, and evil by nature. So this life on earth became a time for them to get ready. It became a time to prepare.

Having become driven by physical desires and evil by nature, this testing period became a time to prepare. It became a season of getting ready.