> They didn’t invest in Siri...
What makes you think that? They insisted on Siri for so long and even made a big deal of Apple Intelligence in WWDC.
Then Apple threw the towel and waved the white flag with regards to Siri and replaced their efforts with third party AI.
Because Siri didn’t seem to change over time. If they worked on it over the past decade it’s not to the point where it was visible to users.