Trump was handed the means to his re-election. A crisis that - if responded to properly - could have united his base + undecided voters behind him.
... he lacks the ability to admit mistake and move on from it. Trump had his chance for a mulligan. But he never took it. He insisted he was right all along and he will have no one to blame but his own ego if he loses in November. All he needed was a little bit of April humility. We are on the doorstep of July and he is still "Wishing the virus away".
The GOP reinforced Trump's bad tendencies, with its anti-science and anti-expert stances. Believing the gov't can't do anything right and staffing the gov't with unqualified hacks. And desire to make everything a partisan issue.
So the Trump Admin naturally failed because they don't believe in experts, science or good government, so they were completely unprepared.
But I agree, Trump had many opportunities to say that the Coronavirus doesn't see Democrats or Republicans or Red or Blue states, that we're all in this together and united we will defeat the virus. It's a national emergency and we will rose to the occasion, etc. A chance to act Presidential and non-partisan. Follow the advice of the experts. Strict lockdowns, tons of aid for those put out of work. Then reopen 10-12 weeks later, when states meet the (now thrown away) guidelines, with plans for testing and tracing in place.
I just think there were too many mental blocks for Trump, the GOP, and right-wing yahoos to overcome. They proved themselves selfish, and uncaring and irresponsible and just plain bad citizens. Became a danger to themselves and others.
As you noted, Trump's tendency has always been to double-down and dig in and never admit a mistake. It's just hard to see what Trump actually expected short of the virus just magically ending. Maybe he believed the analogy to the common flu too much.