First, he was running for POTUS. Returns are usually released, and for good reason.
Two, he lied when he said he would release them after a routine audit. That was over two years ago.
Three, there is substantial evidence of him pulling various scams and engaging in fraud over a long period of time.
Concerns about the financial dealings of POTUS are perfectly reasonable and appropriate, especially when he promises to release the documents, then does not.
I'll remind you:
View attachment 170874
He promised to release the returns. He should keep that promise.