Why would voting Class A Google stock (GOOGL) be selling for less than non-voting Class C stock (GOOG)?

Class C's liquidation preference should be above Class A. And as you mentioned, Class C is better protected. If you don't have any voting right to protect yourself, you must have more contractual rights to protect yourself. So security concern is the reason.

This seems indicate that the voting right for each share is less worthy than liquidation preference, at least for this time.

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With some googling you could find the top results saying that the bankruptcy probability of GOOG is 1.0% or 2.0%, which is significantly lower than the bankruptcy probability of an average US listed company. GOOGL trades about 0.2%-0.3% higher than GOOG, which seems be taking account of the 1.0% bankruptcy risk. Additionally, during the COVID, the bankruptcy risk of many firms have been increased.

Google buys back class C shares, so as their buy back programme has expanded the value of C shares has risen disproportionality to Class A shares, and will continue to do so as long as they keep buying back only one side of their share class.