Um, pressure drives flow from regions of high pressure to regions of low pressure.

Also, Betz's law isn't a law to maximize efficiency. It tells you that because fluid has to leave the back of the wind turbine, it has to have some energy. It can't move at zero velocity. It's impossible to extract 100% of the kinetic energy from the flow for this reason. Betz used a simplified but reasonably accurate model of how a wind turbine works to derive a limit on exactly how much kinetic energy can actually be extracted, even from a perfectly efficient turbine, to be compatible with the fact that the air has to go somewhere.