A few things to casually point out:

EV batteries are mandated by law to have an 8 year, 100K mile warranty. It's fair that you'd want it to last significantly longer, but if these things were built to go kaput immediately after with very little buffer from the warranty period, you're risking a lot of "below average" batteries having to be replaced under warranty - not to mention the reputation of these companies being absolutely shot as they ramp up EV production if they all went out immediately after.

Most modern EV batteries are built with a battery management system. Basically a heating and cooling system and such that you don't see in consumer electronics very much, meant to keep the battery system happy and healthy. The biggest exception to this is the Nissan Leaf, which is based on painfully outdated designs that never really improved from when they first came out almost 15 years ago. Many of those cars have cooked batteries and you would be right to be concerned about it.