Why does an airliner use high thrust during its takeoff roll even though it will later land at a much slower speed?

Answer: It gets the plane fast enough to lift off and climb if something goes wrong.

It gets the plane fast enough to lift off and climb if something goes wrong. ✓ — Right. Near the runway the plane is slow and has little room to trade altitude for speed, so thrust must quickly gain airspeed and climb margin. Lift rises with the square of speed, so a small speed shortfall can mean a much larger lift shortfall. Flaps and slats later reshape the wing for low-speed landing, which is why landing can happen at a slower speed.

It pushes air under the wings so the blast pressure lifts the plane. — Almost, but the engines do not lift the plane by inflating a pocket of air under the wing. Wings make lift from their shape, angle, area, air density, and speed through the air; engine blast does not need to pack the runway under the wing. Jet blast is visible and loud, while the pressure pattern over the wing is invisible, so this misunderstanding is easy to form.

It tries to reach cruise speed before liftoff so the climb is shorter. — No. Takeoff thrust is not meant to reach cruise speed before the airplane leaves the ground; cruise happens much later, high above the runway. Thrust does help the plane climb, but the wing first needs enough airspeed for liftoff and enough climb performance if something goes wrong soon after liftoff. Takeoff is not just starting to move; certification speeds are tied to controllability and climb requirements.