I am sure he thought this would be a different result
To be fair, the social media platform formerly known as Twitter has become more conservative than liberal, but I bet most of Cuban's followers are liberals. The trouble with this sort of question is it plays into their own feelings and their own perceptions of reality.
To some degree, the Arlington Cemetery story is just one example of the larger concepts that we see today. Since people like Mark Cuban can see no good in Donald Trump, they automatically look for the worst in every situation, even something that is objectively good. Gold Star families invited Donald Trump to come pay his respects to their fallen loved ones and even expressed a desire for the event to be photographed. Without any regard for the families or those suffering, the billionaire and his liberal friends all decide that Trump must be doing a bad thing, even as everyone involved believed it was good. How they come to see it as a bad thing, of course, is demanding that it was not really a Gold Star family event, but rather a political rally or fundraising event. The rules are fairly simple, and despite what anyone else might suggest, the memorial service was not a Donald Trump event, much less a political rally or fundraising event. This no different from any military funeral where dignitaries such as the President and Vice Presidents are asked to attend. These events are almost always photographs (and examples of Biden and Harris being photographed in Arlington cemetery are all over the internet today).
So in fact, wasn't Donald Trump doing a good thing by supporting these families and hasn't it been rude beyond all belief that Harris and others are trying to ruin the event and cause the Gold Star families more grief. Why would anyone see the former as the bad person doing the bad thing and the latter as the good person doing the good thing. It's literally impossible unless you twist reality to meet your own expectations.
Over the course of his life, Donald Trump has been recognized for civil leadership, business leadership, and has even been given humanitarian awards for social outreach. He has been more than generous with his wealth, was the only President to finish his term with less personal wealth than when he became President, and has been a family man through and through. Is he a perfect man? Of course not. But what is there about Kamala Harris that would make me want my kids to grow up like her? She hasn't earned the place at the top of the ticket; she has been a coward when it comes her campaign; and she still behaves like a petulant child when it comes to things like the agreed upon debate. I don't have any idea if she is a good or bad person as we really know almost nothing about her. But she has no history of doing anything good for anyone, other than throwing a whole lot of people in jail for smoking marijuana.
Cuban got schooled. I am sure he believes it was some sort of conspiracy cooked up by conservatives to hijack his poll, but it is what it is.
I’d still vote for him rather than these 2