Well, they're incompetent if they need so much hardware for actual fleet actions given the modest non-allied naval power in the world and the more than modest allied naval power in the world.
Even if they did intend this force structure for more purposes than I mentioned; they'd be incompetent in this case. Only incompetents need such a force ratio or spend so much extra wealth of their country on the multiplying the degree of superiority. I don't respect the judgement of incompetents.

So either they're incompetent or the purpose of such a huge navy (and historical precedents) was not to wage major wars against other fleets, but
* impress foreign leaders
* bullying (land attack mostly)


It's hard to come up with a calculation that compares fiscal costs of different forms of major war fighting and still comes to the conclusion that the immensely expensive carrier groups and amphibious forces are more cost-efficient than other forms of assisting allies. Amphibious forces, for example, are at most counterattack forces in a strategic (alliance) defence.


There is of course another explanation, and I'm disappointed that nobody brought this one yet.
We could also explain large navies with an uncontrolled, accidental development and a lot of institutional inertia.
That would kinda lead to the "Niiskanen's bureaucrat" concept, of course.