Well, I still doubt he read them all.

As a German native speaker, I have listened to almost all of the publicly available Hitler speeches, and I found it incredibly hard to keep paying attention. It's as bad as Mein Kampf - just weird sequences of relatively incoherent segments of his twisted world views. Very hard to follow.

And Trump is well known for his extremely short attention span. I would be very, very surprised if that man managed to read even a single Hitler speech from start to finish in one sitting.