So it is always notable when a writer tersely drops conjunctions altogether, and fires off a staccato series of statements, assertions, or exhortations.
Our passage is an example today. Such a clause is called an asyndeton; the plural is asyndeta. There are three asyndeta in Hebrews 2:7-8. I can make the reading more arresting, the points blunter or more emphatic.
I think they're best seen in this case by removing verse numbers and breaking them up on separate lines. I number the asyndeta, thus:
διεμαρτύρατο δέ πού τις λέγων·
τί ἐστιν ἄνθρωπος ὅτι μιμνῄσκῃ αὐτοῦ, ἢ υἱὸς ἀνθρώπου ὅτι ἐπισκέπτῃ αὐτόν;
1. ἠλάττωσας αὐτὸν βραχύ τι παρ᾽ ἀγγέλους,
2. δόξῃ καὶ τιμῇ ἐστεφάνωσας αὐτόν,
3. πάντα ὑπέταξας ὑποκάτω τῶν ποδῶν αὐτοῦ.