Sorry, you are talking rubbish! Conor was 18, when he made his mixed martial arts debut. So most prob started training for mma a few years before. He done boxing as a kid, stop trying to make out that he has all this boxing experience!
When you go into mma, you do not just focus on boxing! You have many different martial arts you have to learn, hence the reason why a boxer will always be better on their feet than a mma fighter!
You say that Conor had all these sparring matches building up to the fight, that simply is not enough! You are making it sound like it should have been easy for Conor to adapt go boxing, when in reality, it can take years, and a lot of professional 12 round fights to master your technique, pacing, head movement etc
There is a reason call boxing a sweet science!