After all, for pirates, these islands are truly great to plunder: low defenses, wealthy, and unable to escape. Would they rather not target these islands and instead challenge the navy or their fellow pirates? The former would bring them major troubles with little gain; the latter might even be poorer than themselves.
Following their plunder, pirates naturally proceeded to engage in reckless spending, as there was no point in saving money for a coffin, having chosen this line of work. Thinking of retiring peacefully was out of the question.
On the other hand, after Gu Shanhai brought the Child of Destiny's Divine Phase Investiture of the Gods to an uninhabited sea area, he directly manifested his true form.
A breakthrough definitely required his true form. It didn't matter that he wore transformations allowing him to change size or shape; it was just that during the breakthrough, it would affect his self-monitoring since his state was disguised.
