I agree with aterpster. But to unpack that a bit more for a journalist:
When a small twin-engine plane has an engine failure, not only does it lose half its power, but the remaining power is now asymmetric, since the good engine is out there on one wing, to one side or the other of the center of the aircraft.
Like a slow-motion catherine-wheel, the asymmetric thrust tries to push the plane in a circle, or "yaw," towards the failed engine, as aterpster says. In addition, the propeller blade on the failed engine is now, for all practical purposes, just a big aluminum board dragging in the slipstream, adding to the yaw force, and also degrading the overall ability to maintain flying speed.
Bizjets with engines (usually) on the fuselage near the tail, still produce asymmetric thrust if one engine fails, but not as much as a plane with engines way out on the wings and far from the centerline. A small light piston-engine prop twin is actually trickier to handle if an engine fails.
Learning to handle an engine failure, and maintain control with the abnormal aerodynamics in a twin, is the core of training for, and receiving, a "multi-engine" rating.
The pilot has to be very fast off the mark in making several adjustments to the controls: identifying which engine has failed (fairly easy with a C310 - the engines are right outside the windows); rudder away from the failed engine to counteract the yaw; "feathering" the failed engine's propeller blades so that they are twisted thin-edge-on to the slipstream for minimum drag; some aileron (roll or bank) away from the failed engine. While also maintaining flying speed with half-power, yet not descending into the ground. And dealing with the "startle" factor - "What the heck just happened!?"
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Other factors, not specific to twins, that would degrade airplane performance and reduce the margins with (or without) an engine failure:
Elevation - the air in Columbia (elev. 2000+ feet) is less dense than sea level. Less air for the engines to breathe (less power), less air to lift the wings. That reduces the margins for error in the case of some other problem.
Density altitude - hot air is even thinner. If it was a hot July afternoon (80°+), the effective elevation at Columbia (air available as above for flying) might be as much as 4000 feet. Another bite out of the margin for error.
Weight - 4 people in an C310 is not excessive by itself. But if there was a full fuel load and degraded performance due to air temperature and elevation....
Ground effect - within a wing's length of the ground, a cushion of lift develops between a wing and the ground. It is not at all unknown for overloaded or underperforming aircraft to lift off from the runway successfully with that extra "ground" lift - at a speed that is not enough to continue flying "out of ground effect." Result - you are off the ground, but unable to climb beyond 10s of feet, unless you can continue to accelerate (which may require a slight descent to pick up speed).
One can probably assume a jet pilot understood all of those very well, and did the appropriate "reduced performance" calculations that he does every day in his professional work.
But he might have been close enough to the safe margins that a failed engine put him outside the envelope.