There is a huge difference between a 1.4% failure rate and a 40% failure rate.
NASA got a whole lot of science done with those missions.
Also, it's not as though the Russians and Soviets didn't have their share of in-flight fatalities as well.
The shuttle was capable of missions that wouldn't have otherwise been possible. It also ferried more people at once.
That said, the shuttle was severely underutilized and hence costed a lot more than it should have.
I don't think so, really.
Columbia didn’t explode in the sense of a massive detonation of something onboard. It had a hole punched in the wing during take off. During re-entry, hot gasses penetrated the wing and led to failure of the control surfaces, and the resultant loss of control (it was gliding at this point) caused heating and dynamic pressures that eventually led to vehicle break up .
Strictly speaking, the Challenger also wasn’t destroyed by an explosion. The failure of an O-ring on one of the Solid Rocket Boosters led to pressurised burning gas destroying the attachment hardware the held the SRB in place. The SRB ripped away causing the entire stack to tumble. Challenger ended up at the top and had its back broken by aerodynamic forces at the same time as the thin skin of the external fuel tank shredded, leading to a sudden massive burn of the fuel it contained (which caused the ‘explosion’ effect so visible from the ground). The crew compartment 'survived' all this and continued ballistically upward before falling back to the sea where it was destroyed on impact, killing the crew.