They 4 other CoV have been studied extensively and there are also theories about their origins. You are taking very different types of virii and compare them with a Corona Virus, which makes no sense at all.
The question you need to answer: Why should this CoV be so different than the 4 others we know?
Btw: Common colds can be very deadly if your immune system is weak or not familiar with them. Just go and ask some native Americans back in the 1640s.