Trump should not dictate to Ukraine how it should act. But on the other hand, why does he dictate?

Because Zelensky has become dependent on the United States of America, on Trump himself.

He may stop dictating, but first Ukraine will be deprived of intelligence, and then of weapons. Things it desperately needs, and perhaps not just weapons.

The lesson is: do not become dependent, especially on major powers.

Be friends with them. Do everything necessary to ensure that they maintain friendly relations with you.