The Leaf is handicapped by its battery cooling system. Air cooled requires heat tolerant chemistries. Dropping in the likely cheaper, but less tolerant cells used in the Ariya is just asking for a repeat of the early Leafs. Adding liquid cooling makes it a bigger undertaking that likely is better done on a redesign. Using an ICE platform can save production costs in that the EV can be assembled on the same line as the ICE model. That was Toyota's plan with eTNGA. But there is a limit there. An assembly line can only make so many units. With the compromises in using an ICE platform for a BEV, it isn't an efficient way of making the EVs when they are the majority built. An EV platform built on a dedicated line leads to lower production costs, and for an affordable model with low margins, that is more important. Of course building those new lines takes time, so why not continue making some of the older EVs until then. GM got a deal of batteries from LG for the Bolt. It included buying the other EV components from them. Switching to an Ultium battery would likely require also switching to an Ultium drive train. Since Ultium production is really just starting to ramp up, it would probably lead to cost increases to use it in the Bolt at this time, assuming the supply was there to support it. It could have been done at a later date. Then the Bolt runs afoul of GMs current EV naming strategy. Seeing how GM it going to use the Bolt line for EV pick ups, I think the car's demise is more about resources for other models than the car itself. The Volt's final cause of death was the closing of the plant it was made at because the other cars made there were being cancelled, and moving its production to another location wasn't worth the investment. Same vibe.