Intent was related. Remember, the full statutory Curruption investigation took place and was determined complete in MAY BY DOD.
SINCE that point, any claim of Trump interest in the subject ( rooting out Curruption before releasing money) should have corresponding action by him to verify or supplement what was done.( Forgetting for a moment the legality of Trump imposing requirements not contained in the legislation).
So it is always pertinent to intent to make sure that log of action( or inaction) is complete. From it one can deduct objectively the intent to investigate " Curruption" vs intent to investigate a political opponent.
And the BONUS…
If Trump released the money immediately upon obtaining knowledge of the WHISLEBLOWER complaint, that is strong circumstantial evidence in itself. But if Trump did nothing to objectively investigate Curruption preceding, you have removed Curruption investigation as a reason for his delay. You are left to suggest Trump incompetent, or inept, or lazy , or full of it).
To answer the How Question:
Circumstantial evidence testified to as a foundation is HOW. FOR example: I heard what sounded like Thunder, a guy then walked in wearing a soaking wet raincoat from the front door.
My presumption is it has been raining outside. Even if I didn’t go out, see it raining standing in the rain getting wet. The jury can use it’s common sense. It need not accept the possibility of mass hypnosis, or a rainmaking/ thunder machine just happened to be there.