This guy writes and thinks well. Follow his reasoning here -- essentially Clinton is closer to Republican establishment thinking than either Trump or Cruz is. So they (The Republican establishment) are either being sneaky or stupid. Hard to tell which.
There's a whole bunch of short videos, so if they don't come through, follow the link and view them there if you want to.
Find it here: http://benjaminstudebaker.com/2016/03/31/does-the-republican-establishment-want-clinton-to-win/