An expression meaning that a result or situation is to be expected — equivalent to “no wonder” or “which isn't surprising.”
彼は毎日深夜まで働いている。そりゃあ、それもそのはずだ。
He works until late every night. Well, no wonder (that's to be expected).
テスト勉強を全くしていなかった。結果が悪かったのもそれもそのはずだ。
I didn't study at all for the test. It's no wonder the result was poor.
急に気温が下がった。風邪をひく人が多いのもそれもそのはずだ。
The temperature suddenly dropped. It's no wonder many people caught colds.