Right about “motive” which is not an element although, as you say, it can help support the malice element which requires intent or recklessness about the falsity.
However, the requirement for malice is not necessarily the public figure status of the plaintiff but is raised as a required element to prove defamation if the defendant raises a Constitutional first amendment defense.
So prudence says that Trump should be ready to prove malice in anticipation of such a defense. I don’t think malice would be hard for Trump to prove. Probably proving the falsity would be harder.
Proving someone acted in a knowingly false manner is a high standard required for proving malice.
Trump can do it but it would require some very intense depositions and then cross examination in court with state of mind likely coming into play too.