Speaking scientifically an asteroid that size would've collapsed on earth faster than they think because of the massive gravity it has.
On the mission to destroy it, I'm surprised they tried to destroy something from the surface instead of from the core lmao.
The 2nd attempt to do it is even weirder because there is supposed to be gravity on the asteroid to collect the rubble or leftover after the 1st mission also all the stuff they could humanity only send 1 guy to destroy it, kek.
To be honest even destroying it wouldn't solve the issue as the debris would still fall on Earth and prolly erase all of humanity
A solution though could be to send a nuclear rocket or something on the side of the asteroid as soon as it is detected in outer space, to give a little nudge to its trajectory and make sure it doesn't get trapped in Earth's gravity field