The issue with support is often not what they believe, but what they feel it will do to their votes. Obama and Clinton feared what such support might do to their support and getting votes they needed. They are both methodical and cautious, sometimes a bit too much.

 
If Trump is nothing else, it is brazen. Sometimes he does this to the point where it hurts himself, and it takes a lot from his advisors to try to reel him in. But while you can argue that I shouldn't take away from this what he did, and I get why you would, I do not believe for one minute he did this to show support for the LGBTQ. I moreso he believe he did it for himself. He's done way more to hurt the LGBTQ community. He's rolled back numerous protections, supports abolishment of gay marriage, and wants to pratically do away with recognizing that Transgender people exists, as he argues there are only two sexes.

 
More on Obama since you name dropped him. He worked with Congress to pass and sign into law the Matthew Shepard and James Byrd, Jr. Hate Crimes Prevention Act into law. He set up an anti bullying task force specifically focused on LGBTQ youth. Obama issued a directive on same-sex domestic partner benefits, opening the door to them getting benefits when partnered. This list can actually get really long, but hopefully I have made my point.

 
What's my point? One appointment is not a fair indicator of support. You need to dig deeper. When you do, the difference between Trump and Biden, or Obama, or Clinton, is crystal clear.