You will probably hear on many sites like this, about the importance of show don’t tell. Something that I think gets undersold too often to writers, especially new writers is “Listen don’t tell”
You are looking for an audience, or have already gained one. Either way, if someone reads your story and is unclear about something, they are speaking for many people who don’t have the courage to tell you. As the author you are omnipotent, You know why Bill would risk his life for someone he doesn’t know when he is otherwise stone cold. It is obvious that at some point in his life someone did this for him. Obvious to you anyway. Don’t be afraid to start a conversation with the unclear reader. Don’t just tell them why he did it so they are clued in, that won’t make you a better writer. Listen to what they have to say and throw your ego out the window. There are key words that may help you realize what you did wrong the first time so you can edit it and not make the same mistake again. If you write a murder mystery and someone feels you cheated because you didn’t make a clue transparent to the reader, they feel misled and are less likely to read the next one. You don’t need to paint neon red signs pointing to every clue, but make sure they get some form of notice.
I try to listen to other authors advice about my work, but I put even more time into listening to the readers that don’t know me, other than my work. They are more likely to be honest when something didn’t work for them. So share your stories with strangers, they can be your best teachers.