Reliance upon Allah does not mean abandoning practical means. Work, planning, consultation, treatment and appropriate precautions all matter. They are not independent sources of ultimate power: outcomes remain under Allah's decree.
Two situations
1. A learner neglects preparation and merely asks for success. This overlooks a real responsibility.
2. Another prepares, seeks clarification and also asks Allah for success. This joins effort to prayer.
In فَاسْتَعِنْ بِاللَّهِ, the preposition بِـ links seeking help to Allah. The expression teaches where the heart should place its ultimate trust; it does not excuse neglecting one's duties.