Yeah... they were looking at what Tesla was selling, and said 'Hey, they make money at the high end, their Model X is very popular and expensive, let's do THAT.'
They were looking at Tesla, who was making batteries, and said 'Hey, they make a profit, and make their own batteries, let's do THAT.'
Meanwhile Tesla was moving to smaller vehicles AND to licensing a lot of battery tech and buying batteries AND to chasing costs down the learning curve 10% per year.
And Ford and GM release large vehicles with their own batteries about 2-3 years after that was a good idea.
They always say incumbents can keep up with the rate of innovation in a new business, nor can they make decisions or plan/build production to stay competitive. I think that pretty much checks out.
The legacy companies would do well to engineer simple (and likely smaller) vehicles, with the goal of getting them to market quickly and in decent scale, and buy batteries from CATL or license the tech. And forget all the 'moonshots' that take 5 years to get off the ground (and miss the Moon, and 'Tesla killers' that by the time they are out are competing with a market that Tesla has wound down.