Every independent clause must have a subject and main verb. In 1, the subject is "all the passengers" and the main verb is "were engrossed". The adjective phrase beginning with "completely oblivious" modifies the subject "all the passengers". It is not necessary for it to have a subject and main verb.

They don't have verbs because they aren't sentences! They are just extra information dependent on the main part the whole sentence. For example, the core of the second sentence is 'A Zimbabwean man slept through the night'. The extra information, 'oblivious to the fact that there was a crocodile under his bed', refers back to the main sentence. It is understood that the subject of the dependent phrase is 'A Zimbabwean man', and it is understood that the verb is 'was'. It's a condensed form of these two sentences: A Zimbabwean man slept through the night. He was oblivious to the fact that there was a crocodile under his bed. We often do this with participles, too: Sunny read the sentences, surprised at the apparent lack of verbs. Sunny read the sentences, wondering where the verbs were. In both cases, the subject and verb 'and she was...' are implied .

Think of it as a rephrased participle clause: "A Zimbabwean man slept through the night, (being) oblivious to the fact that there was a crocodile under his bed." == "..... , forgetting the fact that...". For more information and examples, have a look at page 3 of this document: https://www.csun.edu/~bashforth/305_PDF/305_PDF_Grammar/ParticiplePhrasesAsReducedARelatives.pdf

I think there are these verbs in sentences: were engrossed , slept, there was.