expression
when you get right down to it; as for the cause; originally
Used to trace back to the root cause or original reason for a situation, often implying that the speaker is pointing out the fundamental source of a problem or outcome.
元はと言えば、君が遅刻したのが原因だ。
When you get right down to it, the cause is that you were late.
元はと言えば、私が言い出したことだから、責任を感じている。
Originally, it was something I proposed, so I feel responsible.
「そもそも」 is an adverb/conjunction meaning 'in the first place' or 'to begin with', often used to question the premise. 「元はと言えば」 focuses more on tracing back to the specific cause or origin of a current situation.
A set phrase composed of 元 (origin) + は (topic marker) + と (quotative) + 言えば (conditional of 言う, 'to say'). Literally 'if one says as for the origin', it is used idiomatically to mean 'when it comes to the cause' or 'originally'.