Are there any books I can read to help me get more educated on understanding ahadith? I'd love to read some if you have any that you can send via link.

And also, where can I find books where the marja’ explains why he came to such-and-such verdict on a topic?

Some books:

Yes, the Maraje’ explain how they derive each ruling. They do so in their Fiqhi encyclopedias. They are in Arabic (not English). If you read Arabic, you can access the encyclopedia of any scholar online and read how they derive laws from hadiths. All the main Maraje’ today have such encyclopedias and they are accessible online