The Doctor answered as many of Sophia’s questions as possible. Clearly the Monk had planned this trap for some time and, as usual, he’d given no thought for people like her who’d be hurt in the process.
But why switch him with his first self? Sophia said the Monk always intended the attack on the Doctor’s fifth incarnation as his primary one. And what had Vicki said? That he was more fretful than her Doctor?
Evidently the Monk had taken advantage of his uneasiness and uncertainty to steal his life. Now the Doctor had six days to win it back.