You miss the point. The Israelis know best how to protect their borders.
Rice pressured the Israelis to give up that protection.
She sided with those who want to destroy Israel and made it easier for them. This time they failed. They could just as easily have succeeded.
That's the only point.
Before the handover of Gaza, access to Gaza from Egypt had been a problem all along the Sinai border to the point of tunnels being constructed.
Assuming that maintaining security along the entire Gaza border was untenable, by establishing what would appear to be an open door, with proper monitoring (which is what apparently failed), Israel can be more aware of what is coming into Gaza through this "friendly" gate. All of Israel's access points along the "green line" fence face threats on a regular basis, and it would not be unusual for bombs to be (attempted top be) smuggled across at any of them --- especially out of Gaza--- regardless of who monitors the Sinai border.
Ideally, Israel would still be in full control (were they ever?) of Gaza and destroy the terrorist militants once and for all, but this hasn't happened up until now, and I don't anticipate it being a long-range/long-term option.
Maybe. How many innocent Israelis have been killed in the last several years by homicide bombers?