Nokia was once the largest mobile phone company in the world but failed to keep up with changing market trends. It fell behind competitors by relying too heavily on the Symbian OS and making a misguided deal with Microsoft. As smartphones became popular, Nokia was slow to innovate and lost market share. It also struggled to implement an effective branding strategy across multiple product lines as Apple and Samsung unified their brands. Nokia's complacency and failure to adapt caused it to decline significantly.