2Peter 2:21, 22 is based of Prov. 26:11 with a distinction that can easily be over-looked. Both Scriptures mentions an un-clean animal that is consistent and predictable: then a fool and his folly is mentioned. Both Scriptures are quite relevant in this season, so that we, do not repeat mistakes of others.
A dog is considered to represent contempt or abasement; a male cult prostitute, a pagan sacrifice[Strong's].
Vomit represents something ingested, and rejected by the mind, stomach, or our Lord.
Fool is a stupid fellow, dullard, simpleton, arrogant one[Strong's].
Folly = foolishness.
The Word states that "there is no new thing under the sun". "As the days of Noah were, so shall the end time be". They were actively involved in much wickedness during Noah's day - much of it was authorized by the leaders. Here we have come full circle with abortion, same sex wedding etc. that is required by the state.
Prov. has said "a dog" which is general, yet a fool and his folly are comparable. The fool has ingested foolishness, that is unacceptable-yet he returns to it. Apostle Peter has narrowed it down to "The dog".
The One-World-Political-System is up and running. "The dogs" that uphold this System walk after the flesh in the lust of uncleanness, and despise government[dominion] etc.. These Blind leaders and Blind followers will continue to double-back: let us not follow them for they are predictable. And so are the consequences.