Those in positions of authority have realized the situation. أَدْرَكَ أَرْبَابُ النِّعَم.

أَدْرَكَ أَرْبَابُ النِّعَم.
أي جاء مَنْ له اهتمامٌ وعناية بالأمر.
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Those in positions of authority have realized the situation.
That is, someone with a stake in and concern for the matter has come forward.
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المثل «أَدْرَكَ أَرْبَابُ النِّعَم» يُقال عندما يحضر أصحاب الشأن أو المسؤولون أو أصحاب المصلحة والقدرة على رعاية الأمر والاهتمام به، فيزول القلق لأن الأمر صار بيد أهله.
وأقرب المقابلات الإنجليزية هي:
"The cavalry has arrived."
«وصلت النجدة.»
أي حضر من يستطيع تولي الأمر وإنقاذ الموقف.
ومن التعابير الأخرى:
"The right people are on the job."
«الأمر في يد أهله.»
"Help is at hand."
«العون حاضر.»
"The experts have taken over."
«تولى الخبراء الأمر.»
وإذا أريد مثل إنجليزي مأثور قريب من المعنى العام، فأنسب مقابل هو:
"The cavalry has arrived."
أما إذا كان المقصود التأكيد على أن الأمر صار بيد أصحابه وأهل العناية به، فالتعبير الأقرب هو:
"The matter is now in good hands."
«الأمر الآن في أيدٍ أمينة (أو في يد أهله).»
وهذا الأخير هو الأقرب إلى روح المثل العربي.
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The proverb
"The cavalry has arrived" is used when those in positions of authority, responsibility, or those with a stake in the matter and the ability to manage and attend to it are present, thus allaying the anxiety because the matter is now in their hands.
The closest English equivalent is:
"The cavalry has arrived."
"Help has arrived."
Meaning, those who can take charge and resolve the situation have arrived.
Other expressions include:
"The right people are on the job."
"The matter is in the hands of those who are qualified."
"Help is at hand."
"The experts have taken over."
If you want a more general English proverb that captures the same meaning, the most suitable equivalent is:
"The cavalry has arrived."
However, if the intention is to emphasize that the matter is now in the hands of those who are qualified and capable of handling it, the closest expression is:
"The matter is now in good hands."
"The matter is now in safe hands (or in the hands of its rightful owners)."
The latter is closer to the spirit of the Arabic proverb.