Why does a strong presidency necessarily sap power from Congress?

Presidency and congress should not have power over each other, but when the presidency is too strong it distorts the power of Congress, because congress seems weak in the face of presidential power.

Explanation:

However willing to do what he wants, the chief executive (the president) needs the support of the majority of the National Congress. This is because congress and social security must have the same level of power and influence in the country, so that one can control the other fairly and equitably.

When the president is strong, highly popular, the influence and power of the presidency grows. A very strong presidency ends up controlling the congress unevenly, with this the Congress shrinks and has its power diminished and weakened in relation to the presidency. But when the presidency leaves room for the other powers, Congress has a chance to rise again.