Just hours after Grok 3 took the top spot from ChatGPT in the Apple App Store, OpenAI’s rapid growth suggests the world’s most popular AI company isn’t slowing down, even with competition heating up from China’s DeepSeek and Elon Musk’s xAI Grok. In an interview with CNBC, OpenAI’s chief operating officer, Brad Lightcap, shared that OpenAI had reached 400 million weekly active users as of February. That’s a 33% jump from the 300 million reported in December—figures that had not been made public until now. “People hear about it through word of mouth. They see the utility of it. They...