Calculate angle (degrees) in Python between line (with slope x) and horizontal
The line goes in x-direction from 0 to 9 and in y-direction from 7500 to 9500. Therefore your slope is only 0.00788091068301 and not 0.57 for about 30°. Your calculations are correct, but better use arctan2:
angle = np.rad2deg(np.arctan2(y[-1] - y[0], x[-1] - x[0]))