Weather is driven by atmospheric pressure. High pressure and Low pressure systems act just like compressed air and vacuums with the added complication that they rotate. High pressure rotates clockwise and low pressure rotates anti-clockwise or counterclockwise.
If you look at a map with a low pressure system you can predict how it will move the same way a wheel moves. A low pressure system moves to the left like a wheel moving anti-clockwise. Hurricane Harvey moved from the Gulf of Mexico left to Texas where it was blocked from moving further left by a high pressure system to the West and North. The wind from the southeast part of the high pressure system met the wind from the northwest part of the low pressure system which was pumping moist air from the Gulf into the cold dry air from the American deserts.
Loads of rain fell as the systems cooperated to stop the movement of each other for several days. Nature caused them and President Trump could not stop them.

A third pressure system, a high pressure system to the North and East of the Harvey low pressure system forced the low to stay put over the eastern gulf.
Science explains how things work so now you know some of the science behind Hurricane Harvey. It had nothing to do with President Trump regardless of how the Democrats, the progressives and the American Left try to mislead you into thinking otherwise.
In fact there is a considerable basis to blame the intensity of the pressure systems on the lack of particles in the atmosphere, particles that would have attenuated the sunlight that could have weakened the pressures; particles removed by controlling large fires in nature and by lower amounts of volcano activity.