Compare these two snippets. I added color to highlight my point.

First, Bereishis 14:19-20. A massive regional war just completed, and Avraham joins the kings he fought with. Malki-Tzedeq the king of Shaleim (the future Jerusalem) and priest of the Kel Elyon (most high G-d) serves food and blesses him:

וַיְבָרְכֵהוּ וַיֹּאמַר: “בָּרוּךְ אַבְרָם לְאֵ-ל עֶלְיוֹן קֹנֵה שָׁמַיִם וָאָרֶץ.
וּבָרוּךְ אֵ-ל עֶלְיוֹן אֲשֶׁר מִגֵּן צָרֶיךָ בְּיָדֶךָ”, וַיִּתֶּן לוֹ מַעֲשֵׂר מִכֹּל.

He blessed him and said:
“Blessed be Avraham to the Most High G-d, Owner of heaven and earth.
“And Blessed be the Most High G-d who delivered your enemies in your hands.”
And he gave him a tenth of all [the booty].

And now, Birkhas Avos, the first blessing of the Amidah:

… אֵ-ל עֶלְיון. גּומֵל חֲסָדִים טובִים. וְקונֵה הַכּל. וְזוכֵר חַסְדֵּי אָבות. וּמֵבִיא גואֵל לִבְנֵי בְנֵיהֶם לְמַעַן שְׁמו בְּאַהֲבָה: מֶלֶךְ עוזֵר וּמושִׁיעַ וּמָגֵן: בָּרוּךְ אַתָּה ה’, מָגֵן אַבְרָהָם:

… Most High G-d, Supporter through good generosity, Owner of everything, Who remembers the generosity of the forefathers and brings the redeemer to their children’s children for the sake of His Reputation, with love.
King, Helper, Savior, and Protector.
Blessed are You Hashem, the Protector of Avraham.

And in case you find comparing “Qonei shamayim va’aretz” and “Qonei hakol” a stretch, note that on Friday night, in a shortened repetition of the Amidah, the Chazan does use “Qonei Shamayim va’aretz“. Chazal did consider them roughly identical; although it would be interesting to explore why they changed the expression from “heaven and earth” to “everything”.

To further this comparison, Malki-Tzedek’s titles for G-d — “Keil Elyon” and “Qoneih haKol” — are uniquely found in this story (here and in Avraham’s reply) and nowhere else in Tanakh. They also make very weak theological claims: “Keil Elyon” is true — Hashem is the Highest Power. But it can be asserted by a Canaanite who happens to believe that El is greater than his other deities. Similarly, as the Creator, of course Hashem owns what he created. But to only call Him “Owner” also includes people who don’t believe in creation. These phrases make sense for Malkhi-Tzedeq, who was trying to preach monotheism even before Avraham. (Our sages associate him with Sheim, Noach’s son.) They allow him to build a student base without confronting too many of their beliefs up-front. But they are odd expressions for us Jews to use in prayer — and in fact they do not appear elsewhere in the siddur, either.

I think therefore it’s clear that the Amidah is making reference to Malki-Tzedeq’s blessing. And moreso, a blessing of “אֱ-להֵינוּ וֵא-להֵי אֲבותֵינוּ. אֱ-להֵי אַבְרָהָם, אֱלהֵי יִצְחָק, וֵאלהֵי יַעֲקב — G-d as we perceive Him, G-d as perceived by Avraham, by Yitzchaq, and by Yaaqov” uses terms from a less developed perception of Deity, language of Malki-Tzedeq who attempts to be a priest between idolators and the Creator without confronting his “congregation”.

I am not sure what to make oft this — it’s counterintuitive. Perhaps the point is just that — to identify the lofty conception of G-d the avos discovered with the concept their contemporaries grappled for when they looked at creation. That the G-d of revelation is the G-d of nature.