It looks like the trend started heading upwards before AI took over. Are we sure this wasn't just the way it was heading anyway? Is there a control group that

It looks like the trend started heading upwards before AI took over. Are we sure this wasn't just the way it was heading anyway? Is there a control group that doesn't show the same line? Overall from personal experience TFA's conclusions do seem correct to me, but I want to make sure we aren't confirmation biasing the interpretation of the data.