why did he talk to Bob?

In 2018 Bob Woodward, who was instrumental in getting rid of Tricky Dick, released Book about Trumps Whitehouse. The man in charge commented on Twitter: “The author uses every trick in the book to demean and belittle”

Yet, subsequently he spoke to the author, on the record, on tape (it is always the tapes with Bob) and on 18 occasions.

Why?

If he talks like this to the man who took Nixon down, and would clearly care to bookend his career with two presidential resignations, how does he to talk to people like Putin?