Another interpretation: because the Holy One, blessed be He, appeared to them at the Sea like a warrior waging war, and appeared to them at Sinai like a scribe teaching Torah, and appeared to them in the days of Daniel like an elder full of mercy, the Holy One, blessed be He, said to them, Not because you see Me in many forms - rather, I am He who was at the Sea, I am He who was at Sinai. "I am the LORD your God": Rabbi Hiyya bar Abba said, according to each and every matter and each and every affair He appeared to them. At the Sea He appeared like a warrior waging war; and He appeared to them at Sinai like a scribe teaching Torah; and He appeared to them in the days of Solomon according to their deeds, "His appearance is like Lebanon, choice as the cedars" (Song of Songs 5:15); and He appeared to them in the days of Daniel like an elder teaching Torah, for so it is fitting that Torah go forth from the mouths of elders.
One God Seen as Warrior at the Sea and Elder at Sinai
Yalkut Shimoni on Torah 286:6
דָּבָר אַחֵר לְפִי שֶׁנִּרְאָה לָהֶם הַקָּדוֹשׁ בָּרוּךְ הוּא בַּיָּם, כְּגִבּוֹר עוֹשֵה מִלְחָמָה, וְנִרְאָה לָהֶם בְּסִינַי כְּסוֹפֵר מְלַמֵּד תּוֹרָה, וְנִרְאָה לָהֶן בִּימֵי דָּנִיֵּאל, כְּזָקֵן מָלֵא רַחֲמִים, אָמַר לָהֶם הַקָּדוֹשׁ בָּרוּךְ הוּא לֹא בִּשְׁבִיל שֶׁאַתֶּם רוֹאִים אוֹתִי דְּמוּיוֹת הַרְבֵּה אֶלָּא אֲנִי הוּא שֶׁבַּיָּם אֲנִי הוּא שֶׁבְּסִינַי. אָנֹכִי ה' אֱלֹהֶיךָ, אָמַר רַבִּי חִיָּיא בַּר אַבָּא לְפִי כָּל עֵסֶק וְעֵסֶק, וְכָל דָּבָר וְדָבָר, הָיָה נִרְאָה לָהֶם, בַּיָּם כְּגִבּוֹר עוֹשֵׂה מִלְחָמָה, וְנִרְאָה לָהֶם בְּסִינַי כְּסוֹפֵר מְלַמֵּד תּוֹרָה, וְנִרְאָה לָהֶם בִּימֵי שְׁלֹמֹה לְפִי מַעֲשֵׂיהֶן (שה"ש ה, טו) "מַרְאֵהוּ כַּלְּבָנוֹן בַּחוּר כָּאֲרָזִים" וְנִרְאָה לָהֶם בִּימֵי דָּנִיֵּאל כְּזָקֵן מְלַמֵּד תּוֹרָה שֶׁכֵּן נָאֶה תּוֹרָה לִהְיוֹת יוֹצְאָה מִפִּי זְקֵנִים.