The impedance of a half-wave antenna at its centre is low, because at this point:

According to Ohm's Law, electrical impedance is the ratio of voltage to current (Z = E / I). In a resonant half-wave dipole, the RF standing wave creates a distinct pattern where these two values are inversely proportional along the length of the wire. At the exact center of the half-wave antenna, the RF current reaches its maximum peak, while the voltage drops to its minimum. Because you are dividing a very low voltage by a very high current, the resulting impedance is quite low (typically around 73 ohms in free space). Distractors that claim voltage is high or current is low at the center contradict the fundamental physics of a center-fed resonant dipole. If the current were low at the center, the impedance would be high, which is characteristic of the antenna's ends, not its center.