How do we understand the narrowing of provision for a religious person when they strive in worship, and the expansion of their provision when they commit sins?

This connection between deviation, disobedience, and the opening of doors of provision is incorrect and a deception from Satan. Piety is the way to attract provision, as Allah Almighty says: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect." So, if a servant finds hardship in provision despite his piety, he should question his worship. Allah may also test him to examine his patience and steadfastness. If he remains steadfast in piety, vast doors of provision will be opened for him, because what is with Allah can only be attained through obedience to Him.