Complex sentence: He has an "impulsive Provençal temperament", which leads him to resign his post at the merest suggestion of criticism, causing his employers to expend a great deal of effort in pacifying him and inducing him to stay on.
Split into simpler sentences: He has an "impulsive Provençal temperament", however, which leads him to resign his post at the merest suggestion of criticism. Much effort has to be expended by his employers in pacifying him and inducing him to stay on.