God had determined to destroy humanity on account of its evil (Genesis 6:7). He did not, however, do so immediately, but indicated that he had given a space of 120 years (Genesis 6:3), time for Noah to build an ark of sufficient size to preserve specimens of each species (Genesis 6:13). (Note that God was mighty to save a remnant from each species without the use of an ark and so could destroy all the earth immediately.) In the time it took Noah to build the ark, people continued to sin and multiply evil on the earth (Matthew 24:37–38), under the instigation of the demons. God was longsuffering (that’s what Peter’s word patience
literally means) toward these people despite their seeing the “proclamation” of what was to come as the ark slowly took shape (Hebrews 11:7). God’s longsuffering-ness also means that Noah was not immediately rescued from the evil pressures around him, and so, as a conscientious child of God, continued to “suffer” at the hands of lawless people, which is the theme of this portion of Peter’s letter.
20 because they formerly did not obey, when God’s patience waited in the days of Noah, while the ark was being prepared, in which a few, that is, eight persons, were brought safely through water.