They have not committed to spending $1.4 billion on an AI initiative.
Rather, the new CEO stated it's a priority, and that they want to do it by investing in themselves and others. And then the article notes that they have about $1.4 billion in reserves that could go towards investments like that.
They are moving on AI in a way that is a priority, and is a concern for a lot of people that think they should still be mostly focused on the web. But I don't think they've said anything that makes them as all in as this implies.
The actual article even says directly:
"While its biggest priority remains growing and investing in Firefox, investing in the rebel alliance is “at the heart of who Mozilla is today,” according to the report on Tuesday. Supporting startups is central to that strategy."
But the summary, and to some extent the headline and intro to the article, imply they've made some all in commitment about AI. But nothing actually says that.