I always thought the hardwired reward for mining, namely, X btc every 10 minutes, is the cause of Bitcoin's wasting electricity.

The electricity used is roughly proportional to the hashrate, which in turn is roughly proportional to the price of btc -- until the next halving, which I think is more than one year but less than 2 years from now.

These halvings of the reward every 2 years (which occur on a schedule set before Bitcoin was launched all those years ago) will some time in the next 10 years (which is 5 halving, representing a reduction in the reward by a factor of 2 * 2 * 2 * 2 * 2 == 32) or 12 years bring the Bitcoin network's electricity usage down low enough that a reasonable person will no longer avoid Bitcoin out of worry that it is bad for the global climate.

Note that this mining reward doled out every 10 minutes is not a transaction fee. E.g., neither of the transacting parties (i.e., neither the sender nor the receiver) pays it.

So tell me again what will eventually kill Bitcoin.