O-rings, and old NASA vs current NASA
The O-ring failure that destroyed Challenger happened because of unusually low air temperature (below the design tolerance of the o-ring) coupled with some sort of design flaw in the seal.
Worse, engineers who understood the limitations which led to the disaster had tried to warn NASA administrators that a launch in such low temperatures would not be such a great idea. As usual the beancounters and PHBs won out over the engineers. The rest, as they say, is history.
The seal blew out at ignition while the Shuttle was still on the launchpad, and then proceeded to burn through during ascent. IIRC, you can see a puff of smoke/debris blow out in footage of the launch. Whether anyone in Mission Control saw it too is a moot point, since they couldn't switch off the SRBs once they'd been ignited. As far as I'm concerned SRBs are entirely unsuited to manned space flight for just this reason.
Comparing the Apollo program to Ares: Kennedy's moon shots were driven by national pride. There was no time for red tape, design by committee, or battling for funding. The goal was to beat the Soviets to the moon, and by the way they have a head start so get cracking!
Today there's no real pride at stake and no drive to "beat someone" so budgets are tighter and the consequences of schedule slippage aren't as embarrassing. "Just another delayed engineering project" is hardly news, whereas "Soviets set first man on the moon" is a historical "what if?" and could have had much further reaching implications.