Often, the market demand moves on from what the company is used to making, and institutional inertia makes it hard for it to respond to that change. Probably th

Often, the market demand moves on from what the company is used to making, and institutional inertia makes it hard for it to respond to that change. Probably the most common reason. It's worth noting that big companies are simultaneously inherently dysfunctional and overfitted on their domain. Change is hard. Sometimes, a company will start taking its position for granted and start optimizing for profitability at the cost of customer satisfaction. They assume their position is secure, while it actually isn't, and then they are dethroned. Other times some bad but reasonable enough decisions turned out not to work so well.