Colliding with a part of a chain train with another cart will not transfer momentum and stops the cart. Even in this case when a powered furnace minecart is attempting to move the train.

1.19.2

So in this case, the furnace minecart is the head of the train, but due to a collision got bumped to the end of the train?
Edit: Ah, I think I got it. The hopper minecart is the head minecart, and the furnace minecart tries to push the train from behind, right?

Yeah, in this case, the hopper minecart is the lead of a 2 cart train consisting of itself and the chest minecart. A full speed, separate, furnace minecart ran into the chest minecart and stopped without transferring any momentum.