But yes, it was illegal. Here's why.
“Solicit” means “to ask for a contribution.” And if something is a “contribution,” then by definition it's “in connection with” an election.
If so, he broke the law.
"Coordinated" means made at the “request or suggestion” of a candidate – that’s clearly met here, since the candidate suggested it.
So the only question left is whether Trump asked Ukraine to spend its resources “for the purpose of influencing” the US election.