With all respect to the sacredness of the Bible there are certain places where the logical mind of a 21.century citizen wonders about their meanings. The first one starts right at the beginning of Elohim in Genesis –  Elohim is “monotheistic in connotation”, but “its grammatical structure” indicates “polytheistic”. That itself presents enormous possibilities of different interpretations and conclusions that a seeker finds among scholars. My knowledge of the Bible is extremely limited so I take it very humbly and I try to understand what I read, taking the Hebrew Interlinear Bible.
1:1 In beginning he created Elohim the Heavens and the air
1:3 And he is saying Elohim he shall become light
1:5 And he is calling Elohim to light
1:9 And he is saying Elohim they shall be flown together the waters from under the heavens…..

For me it feels like a conversation between GOD and Elohim, giving him/them instructions.
There is a theory of the Tree of life or the Ray of Creation that explain the laws of transformation of Unity into Plurality, which is closely connected with the Law of Three or the Law of three principles and could explain both conotations of Elohim. Quoting from ISOM:

Every phenomenon, on whatever scale and in whatever world
it may take place, from molecular to cosmic phenomena, is the result of the
combination or the meeting of three different and opposing forces. Contemporary
thought realizes the existence of two forces and the necessity of these two forces for
the production of a phenomenon: force and resistance, positive and negative
magnetism, positive and negative electricity, male and female cells, red/blue and so on, but they will not take place unless the third neutralizing force is present. If we observe a
stoppage in anything, or an endless hesitation at the same place, we can say that, at
the given place, the third force is lacking. In trying to understand this it must be
remembered at the same time that people cannot observe phenomena as
manifestations of three forces because we cannot observe the objective world in our
subjective states of consciousness. And in the subjectively observed phenomenal
world we see in phenomena only the manifestation of one or two forces. If we could
see the manifestation of three forces in every action, we should then see the world as
it is (things in themselves)….. But we know that we cannot observe the world as it
is and this should help us to understand why we cannot see the third force. The third
force is a property of the real world. The subjective or phenomenal world of our
observation is only relatively real, at any rate it is not complete.
“Returning to the world in which we live we may now say that in the Absolute, as
well as in everything else, three forces are active: the active, the passive, and the
neutralizing. But since by its very nature everything in the Absolute constitutes one
whole the three forces also constitute one whole.
The idea of the unity of the three forces in the ABSOLUTE forms the basis of many
ancient teachings—consubstantial and indivisible Trinity, Trimurti—Brahma, Vishnu,
and Siva, and so on.
They separate and unite by
their own will and by their own decision, and at the points of junction they create
phenomena, or ‘worlds.’ These worlds, created by the will of the ABSOLUTE, depend
entirely upon this will in everything that concerns their own existence. In each of these
worlds the three forces again act. Since, however, each of these worlds is now not the
whole, but only a part, then the three forces in them do not form a single whole. It is
now a case of three wills, three consciousnesses, three unities. Each of the three forces
contains within it the possibility of all three forces, but at the meeting point of the
three forces each of them manifests only one principle—the active, the passive, or the
neutralizing. The three forces together form a trinity which produces new phenomena.
But this trinity is different, it is not that which was in the ABSOLUTE, where the three
forces formed an indivisible whole and possessed one single will and one single
consciousness.
In the worlds of the second order the three forces are now divided and
their meeting points are now of a different nature. In the ABSOLUTE the moment and the
point of their meeting is determined by their single will. In the worlds of the second
order, where there is no longer a single will but three wills.

The will of the ABSOLUTE creates the worlds
of the second order and governs them, but it does not govern their creative work, in
which a mechanical element makes its appearance.
taken from chapter 4 of Ouspensky’s In Search of the Miraculous -to be read by humanity

If we take GOD himself as the ABSOLUTE, it is clear that HE does not create the world himself, HE delegates the plan of the work by his single will to Elohim, to the second order which he created, composed of three independent wills.
So Elohim as a result of HIS Will, divided into three? Could that be why the plural form was used by wise ancestors?