The sale to Lenovo happened 20 years after the introduction of the PCjr.
IBM actually did quite well in establishing the ThinkPad as a distinctive laptop before laptops became as commoditized as desktops. But by the time of the sale, pretty much all Windows/ PC machines were commodities and IBM did not want to be in the commodity hardware business.
(Apple doesn’t want to be in the commodity hardware business either. That’s why it got out of the printer business and the WiFi business. But macOS and iOS mean their primary hardware lines do not have this problem.)
Dave