Complex sentence: For the first time in his life, Rupert's financial position was relatively secure, and he had matured--near-contemporaries described how "his temper was less explosive than formerly and his judgement sounder".
Split into simpler sentences: For the first time in his life, Rupert's financial position was relatively secure, and he had matured. Near contemporaries described how "his temper was less explosive than formerly and his judgement sounder".