Bold emphasis mine.
I don't know to what extent if any the following 2 things had a bearing on the rather quick release of the M4 chip family:
1.) Artificial Intelligence was making the news big, and Apple Intelligence sounded half-baked with a slow roll out.
2.) Qualcomm's Snapdragon chips appeared ready to bring the Windows world similar benefit to those of Apple Silicon on Macs, and while the switch to an ARM processor with partial compatibility with software made for Intel (though apparently quite good) was a concern, Microsoft came out backing it, and 'Copilot' PCs were really making the news.
Since then, Intel brought out Lunar Lake, which if I understand correctly offered similar benefits while retaining full x86 chip-based software compatibility, so if I were shopping for a PC notebook right now, what to buy would be about as clear as mud.
All that major M4 series Mac buzz made the news at a convenient time, plus headed into the holiday shopping season.
Notice the sequence - iMac first, so everybody focused on the M4 chip without the Pro or Max stealing its thunder, then the iMac Mini so the M4 Pro got the spotlight, then finally the MacBooks with the M4 Max option. That's some 'buzz management' right there!