Because gender equality is more important than winning wars. And why not? Seriously. It's not as if the US Armed Forces have been defending the nation or its borders for the last 60 years anyhow.
As the student evaluation and graduation requirements gravitate towards female-friendly subjective homework and classroom attendance standards rather than objective physical standards, we can expect women to increasingly not only complete the Infantry Officer Course, but excel in it. Which, over time, will lead to the consequences explained by Martin Van Creveld and quoted in SJWs Always Double Down:
As Martin van Creveld, the Israeli military historian has noted, the more women enter any professional field, the more men leave it. And as the men depart, so to do the prestige and the economic rewards provided by the field. This creates a vicious cycle that both expels existing men from the field while repelling new men from entering it.
If the universities can be considered a reliable model, we're about three decades away from a majority female Marine Corps. No wonder China is content to patiently wait for its opportunity. This marks the second step in the end of the USMC's historical prestige. Even current female Marine officers understand this.
Permitting women to join the Marine Corps was the first mistake. Unqualified female officers are the second one. But the empire is in decline, and so these events are not even remotely surprising. There will be more unnecessary mistakes in the future and they will be more and more disastrous, until the empire "unexpectedly" crumbles for "no reason at all."