Why did Cradock not abandon Otranto?

Why did Cradock keep the slow armed merchant cruiser Otranto instead of escaping with his faster warships?

Detaching her would expose her to a faster and more powerful opponent. One proposed explanation is that Cradock tried to hold the Germans off until darkness gave the whole force a chance to escape.

Otranto could manage only about 16 knots in the conditions, and a German light cruiser could overmatch her eight 4.7-inch guns. Sending her toward Coronel would expose her to pursuit. Cradock closed toward the Germans while daylight remained, either to fight under better conditions or force them back far enough to gain time. His private deliberations are unknown, but holding them off until darkness offers a plausible explanation for staying with Otranto.