Have seen pictures of Trump with daughter, Ivanka, that are just as bad - especially the one with grown Ivanka sitting on his lap. There are numerous instances on film and not on film, where he speaks sexually about her - does it over and over and over.
When behavior happens over and over and over, it is ingrained in the person; it is part of them, not a passing behavior/comment.
Joe Biden:
Certainly, his wife/other people in his family/people he trusts, have talked to him about it looks bad when he touches/holds onto/kisses little girls/women. Because he still does it, means it is part of him he cannot control just like Trump sees his daughter as a sexual being and has to say it. Both of them want to complete an action with another person or persons and these are the attempts to start that happening.
One time, after seeing Biden next to a grown woman whose husband was being sworn in as an officer of some government job, he put his arm around her shoulder and drew her to him and touched her hair and bent down to her ear and said something. I felt uncomfortable as I saw her darting eyes and trying to move away from him. As a result of that, I did a search on him and there were other times he did the same thing to little girls and grown women. He is never going to stop this.