Can someone explain the thesis to me of how AI will replace cybersecurity, SaaS stocks, etc.? How realistic is this?

Most stocks in these sectors have been hammered lately with the idea that Anthropic will just be able to replace these. I’m struggling to understand what this really looks like and how many companies would want to rebuild this functionality in house through AI tools, which seems to be the presumption of these moves.

Anyone familiar or on the Tech/IT side that can break this down for me?