What is the context and purpose of the chapter, of the epistle? Is it to teach on the Apocalyptic Battleground: Earth in the far future Days of Great Tribulation?
1 Peter 2:1 establishes the context and subject matter: False Teachers introducing False Doctrines and making merchandize of people.
Verse 3 focuses on how these false teachers would use 'feigned words" to make money off unsuspecting Christians. Their judgment, however, approaches and they shall not escape.
Verse 4 begins with "For IF..." He doesn't say "Now, here's what happened." He says IF such and such happened. If requires a corresponding Then. The "then" part of the paragraph is implied and not stated due to the lengths spent discussing Lot. But it is obvious what the then part is: "...then God will not spare these false teachers either."
The SUBJECT of the passage in question is false teachers making money off the unlearned and unwise by promoting false heretical teachings and by using feigned words.
Is it not interesting that Peter here quotes from the book of Enoch (chapter 10, verse 4, to be exact)? A Jewish mythological treatise? And in the parallel passage in Jude, when speaking of these sinning angels, again the Jewish apocryphal (pseudepigraphical) book of Enoch is quoted from? Why do both writers quote a non Biblical Jewish myth, instead of just quoting Genesis, when talking about these sinning angels? Perhaps because they are referencing a JEWISH MYTH PROMOTED BY THE FALSE TEACHERS?
Peter is not giving a didactic, doctrinal dissertation on Biblical cosmology and end of days scenarios. He is making an ARGUMENT against a certain group of FALSE TEACHERS. And uses their own teaching to refute them and their covetous merchandizing of gullible saints.
Jewish exorcists taught that angels rebelled against God, were cast down, but now roam the earth as demons. Sound familiar? They charged money for getting the demons out of your life, your house, your business, etc.
Peter is showing how their own feigned words are self refuting (angels bound in hell cannot be troubling you, because they are bound in hell...). And rather than stopping there, and depending on their own Jewish myth to refute and condemn these false teachers, he turns to Scripture to nail the point home: God is not mocked, the wicked false teachers SHALL NOT escape judgement.
THAT is Peter's entire point.