Divine Passive explained

"The divine passive [is] obvious from the passage [e.g., Rom 3.28; 1Cor 7.23; Gal 5.13; Eph 2.5], due to focus on the subject, otherwise obtrusive, or for rhetorical effect…That God is behind-the-scenes is self-evidently part of the worldview of the NT writers.”
The Basics of New Testament Syntax: An Intermediate Greek Grammar, Daniel B. Wallace.

“[The mode of expression known as the divine passive involves] using the passive voice of a verb to denote the hidden action of God as the agent responsible for the activity…A feature which began as a reverential way of avoiding the use of the sacred name of God [becoming] customary, with an extended usage, on Jesus’ lips. He uses it over 100 times [Mat 5.4; Luke 12.7].”
Approaches to New Testament Exegesis, R. Martin, p. 237.

“[In Col 1.16] the verb [create] and its cognates (BAGD 455f.; TWNT iii.999-1034) are used in the NT only of God’s creation (Foerster, TWNT iii. 1027); the noun may be used (1) of the act of creating; or (2) of the thing created, whether an individual creature or creation as a whole. The aorist ektisthe [“were created”] ‘describes the definitive historical act of creation’, the perfect ektistai [“have been created”] below ‘the continuous and present relations of creation to the Creator’ (Lightfoot, 217); the former simply states something that has taken place in the past, while the latter indicates the abiding significance of that past event: it was created and remains in existence. Lohse (49) sees in the ektisthe a ‘divine passive’, signifying that God is the creator.”
Colossians and Philemon, Robert Wilson, p 136.

“The passive ‘were created’ indicates, in a typically Jewish fashion, the activity of God the Father, working in the Son. To say ‘by’, here and at the end of verse 16, could imply, not that Christ is the Father’s agent, but that he was alone responsible for creation.”
The Epistles of Paul to the Colossians and to Philemon, N.T. Wright, p. 71.

“[Col 1.16] moves from the assertion about the Son as firstborn to say that he is the one through whom the world was created (God being understood as the final source of creation). Two passive forms of the verb “to create” (vv. 16a and 16e) obviously allude to “creation” in verse 15b…Jewish tradition had previously said that God created the universe through his wisdom (Prov 8:22-31; Wis 7:17-24; 9:9) or word (Philo)…God created the world “for” the Son, indicative of a divine eschatological purpose…R. Jochanan (third century CE)…said the world was created “for the sake of the Messiah” (b. Sanh. 98b).”
Abingdon New Testament Commentary – Colossians, David Hay, p. 57.

 “With oti [“because”] Paul adds the evidential reason for these designations of Christ, the reason that was fully known to his readers: “because in connection with him all things (that exist, ta panta) were created”. ‘En [“in”] is not instrumental: “by him were created” (A.V.). It is an untenable idea to say that “in him” means that Christ was the archetype [original copy] who in himself contained the ectype [copy], “all things”, either in the sense that he furnished the pattern for them or that the eternal ideas existed in him (Philo’s Logos). Here and scores of times en means: “in connection with.””
The Interpretation of St. Paul's Epistles to the Colossians and Thessalonians, R. C. H. Lenski, p. 54.

“’All things in heaven and on earth’ were created in God’s beloved Son (v.13), not in the sense that he was the preexistent or ideal archetype of creation but in the sense that creation occurred “in association with” Christ (BDAG 327d) or, better, “within the person of” Christ.”
Colossians and Philemon, Murray J. Harris, p. 40.