It is traditional to make the division as between science asking what & philosophy asking why - between physics, and metaphysics. 'What' questions assume framing assumptions, whereas 'why' questions keep stepping outwards to ask how the framing assumptions can be integrated into the whole of what is known, and to compare to metaphors and sources of inference & a multiplicity of other methods.
I look to 'why' questions in relation to strange loops, which are characterised by tangled hierarchies - where previous systems become elements in a new wider zoomed-out system, elements become subsystems, and feedback loops are introduced - like a shifting self-concept altering a projected future, feeding back into how to be (changing the self-concept or resolution about how to be). These different layers of explanation can use very different explanatory methods, like between physics, chemistry, and biology, which use different narrative groupings. David Deutsch in The Fabric Of Reality gives an example of trying to reduce such a model to the minimum number of explanatory layers or framing methodologies.
This strange loop idea gets away from a foundationalist approach to knowledge which inevitably faces Munchausen's trilemma, and can avoid the limitations imposed by Godel Incompleteness, of being able to make consistent true statements using the element of a system which cannot be proven within the system: because there is no isolated system, they are all tangled (in human subjectivity), and procede not from founding assumptions but backwards and forwards from wherever we are, and include being able to reflect on the whole structure not purely logically but in regards to achieving our intentions and needs. See Donald Hoffman's great work on why we can't rely on evolution to reveal reality to us, and I'd point beyond his examples of our self-serving cognitive biases, to how time seems to be a product of our subjectivity rather than fundamental, it may not be 'out there' but exist as a way for us to make sense of our experiences (we might exist in 4D, with a little pool of light we call awareness moving over the structure, tinkering).