During the journey a man named Uzza touched the Ark of the Covenant to support it and fell dead on the spot (2 Samuel 6:1-8, 1 Chronicles 13:9-10). Here are two questions: 1. Why does God kill for this reason (are there Jewish comments that clarify this point)? 2. According to some scholars this death should not be attributed to god but to the ark itself as it is an electric generator / capacitor (this is obtained from the Hebrew rabbinical literature, is there any evidence? יְהֹוָה֙ בְּעֻזָּ֔ה וַיַּכֵּ֥הוּ שָׁ֛ם) It does not appear to me. Shalom.
In addition to @חִידָה's answer Rashi on the pasuk in Shmuel alef writes:
על השל. על השגגה, שהיה לו לדרוש קל וחומר, נושאיו נשא בירדן, הוא עצמו לא כל שכן:
Because of his mistake. Because of his mistake, he should have expounded a fortiori [as follows:] the Ark carried its own porters in the Yardein, isn't it all the more so [that it is able to carry] itself. (Sefaria translation)
Metzudas Dovid on the pasuk in Divrei HaYamim explains further the failing of Uzzah:
ויחר. על מיעוט האמונה בה׳ לחשוב שיפול ארונו וזה על אשר שלח וכו׳:
And He was angry: On his (Uzzah's) lack of faith in Hashem to think that the Aron would fall, and this is why he was struck down.
Ultimately, as the Malbim points out, it was a lapse of concentration on Uzzah part as he essentially forgot that it was the Aron of Hashem and resultantly lost the fear of G-d - And this was why it was such a big sin as he lost any trepidation for Hashem when he was right next to His Aron Kodesh!
In addition, it is worth noting Radak there who writes that Uzzah was not a Levi and therefore it was inappropriate for him to be in the Aron's vicinity.
"The soles of the feet of the Kohanim were lifted. [They were lifted] from the water to the dry land next to them, and the water returned to their place. The result of this was that the Ark was on this [eastern] side and the Bnei Yisroel were on this [the western] side. Thus the Ark lifted its carriers and crossed over. It was regarding this that Uzzah was punished ‘when he took hold of the Ark,’ for if the Ark carried its carriers, it certainly was able to carry itself."
( נִתְּקוּ כַּפּוֹת רַגְלֵי הַכֹּהֲנִים מִן הַמַּיִם אֶל הֶחָרָבָה שֶׁאֶצְלָם, וַיָּשׁוּבוּ הַמַּיִם לִמְקוֹמָם; נִמְצָא, אֲרוֹן מִצַּד זֶה וְיִשְׂרָאֵל מִצַּד זֶה, נָשָׂא אֲרוֹן אֶת נוֹשְׂאָיו וְעָבַר. וְעַל דָּבָר זֶה נֶעֱנַשׁ עוּזָּא (שמואל ב ו ז) כְּשֶׁאָחַז בָּאָרוֹן, נוֹשְׂאָיו נָשָׂא, עַצְמוֹ לֹא כָּל שֶׁכֵּן )