Why is there is so much fuss about Falcon Heavy exploding on the way?

I don't understand why would they purposely design a rocket having a good chance of explosion during launch. If they are not confident in it, why are they launching?

Looks like a lot of risk and waste of time and money to me.

Who would even try to sit in such a rocket even in future when there is such a high chance of explosion? Do they have a plan to mitigate this risk?