Seems like they could have done this a long time ago. Shoeless Joe Jackson’s been dead since 1951. Pete Rose just last year. I think President Trump’s comments about Pete Rose woke some people up.
I have no inside information, but the longer the Rose-saga took to play out, the more obvious it was that the plan was to induct Pete AFTER he died. Pete constantly lied and misrepresented what he had done after he was caught dead to rights. I think that it was quite reasonable under those circumstances to deny him the right to give an induction speech.