The reason it seems counterinuitive and this is the hard part to change in your thinking........... is that most people seem to think there is a down load on the tail holding up the weight of the engine on the nose and it is balanced about the CG. They forget about the wing lift in front of the CG and that the weight of the motor along with the other airplane components is vectorially summed and becomes the CG. When you sum moments about the CG location the motor is already taken care of. You have just the aerodynamic wing and tail forces relative to the CG to take care of. You can use other locations but the math is more complex and the answer is the same.

The angle of attack of the wing (leading edge up) is 20 degrees. The elevator deflection (trailing edge up) is say 20 degrees. The angle of attack alone on the tail at zero elevator deflection would give a humonguous (tech term) lift. The elevator deflection decreases it. But the balance about the CG must be maintained. If the wing is lifting up and the airplane is in steady flight the tail must be lifting up. It is a simple balance. It is easy to work out.

10 inch wing chord, 20 pounds of lift on wing, CG is one inch aft of the wing 25% point, tail arm from CG to tail is 20 inches.

20lbs x 1in = 20in x Xlbs

X = 1 pound of lift on the tail directed up. It works for any steady state flight condition with zero camber and no flaps (assume no strange fuselage shapes)

For an airplane weight there is an angle of attack and an elevator deflection that allows the airplane to trim out and fly level. When you change elevator from that trim condition, say 5 degrees, to 10 degrees trailing edge up you are no longer aerodynamically balanced for that weight. The airplane rotates until the angle of attack of the wing and tail increase and you probably start climbing at a steady rate. In that climb the tail load is still up. With even more elevator deflection you have reduced the load on the tail enough to loop.

Imagine if you will an all moving horizontal tail and the angle is measured with respect to the wing.

If the wing is 10 degrees angle of attack and the tail is 15 deg leading edge down then the tail load is down.
If the wing is 10 degrees angle of attack and the tail is 10 deg leading edge down then the tail load is zero.
If the wing is 10 degrees angle of attack and the tail is 0 deg leading edge down then the tail load is up.
If the wing is 10 degrees angle of attack and the tail is 10 deg leading edge up then the tail load really up.

What the airplane does at these conditions depends on the airplane weight and stability parameters.

If you add flaps or camber on the wing which make a big enough nose down pitching moment then the tail must counter it and can end up with a down load. Look at how it works. The wing and tail are at say 5 degrees angle of attack and every thing is balanced out in level flight. Lower the flaps and the airplane takes a nose dive and the lift goes up. The angle of attack might even have to go to zero to maintain level flight. The net result can make enough nose down moment that the tail must create a down load. Since the angle of attack of the tail is the same as the wing (zero maybe) it is not creating any forces due to angle of attack. You get the down load from the application of up elevator.

I have carefully ignored what happens in 3 D maneuvers, snaps, etc. There the forces are highly irregular and it can only be determined by watching where the airplanes goes - too hard and too much work.