God's oversight of the world involves a firm commitment to historical justice. Acts of violence and the oppression of innocent people never escape His notice, even when a divine response is not immediate. God actively seeks justice for the blood of the innocent and the weak that has been spilled by oppressors [רד״ק, ביאור שטיינזלץ]. Historically, this specifically includes the blood of the Israelites shed by other nations [רש״י, רד״ק]. This spilled blood is constantly remembered before Him, even if He is patient and delays punishing the wicked right away [מצודת דוד].
Offering a completely different perspective, [אלשיך] looks at the reality of the world through a logical contrast. He notes that God sometimes allows the nations that have harmed the Israelites to remain in power, granting them favorable lives in this world even though they act against His will. If God remembers these nations favorably, He will certainly never forget the painful cries of the exiled Israelites who actively strive to do His will.
There is a subtle but important distinction between God remembering and God not forgetting. Remembering often implies a return to awareness after a period of seeming forgetfulness, awakened by a specific trigger such as the demand to avenge spilled blood. However, the concept of not forgetting indicates that the cries of the victims never actually slipped from His memory at any point [מלבי״ם]. These victims are often identified as both poor and humble. The duality of these traits stems from the reality that the impoverished and weak in society are usually the ones who possess genuine humility [רד״ק, המאירי]. They are people who conduct themselves with proper modesty [ביאור שטיינזלץ, מצודת ציון]. Ultimately, God guarantees that the desperate cries of these humble individuals will always remain in His active awareness.