I didn't get what "he was all business" means.

“I had the Reagan guy, and he didn’t seem sadistic or threatening,” said Ruth Marone, 18. “But he was all business. I didn’t get that Robin Hood vibe or anything like that.”
Hi Job,

'All business' means 'serious', or 'only concerned with whatever business is to be transacted'. We often use the phrase about someone who is unwilling to joke or chat during a business discussion.

In your quotation, it seems to mean that Reagan was just normally occupied with whatever business he had with Ruth Marone; he was not strange about it.
Thank you.