I wasn't referring to illegality with the "hijacked" term, I meant it as in "jumped into a vehicle that really didn't fit him and steered it somewhere it wouldn't normally go".  

And no, they didn't "overwhelmingly" choose him.  In fact, "they" wasn't even entirely Republicans (thanks to the stupid policy of open primaries in some states).  

Trump's nomination never would have happened with a reasonable number of candidates in the race.  When you dilute the field so much with 17 candidates, it creates a scenario where the mainstream candidates may cancel each other out and fail to have consolidation around one.  Which is exactly what happened.  It allowed Trump to hang around with relatively small support.  Even by the end, most Republicans didn't want Trump as the nominee. But they were stuck by then from their failure to consolidate around one mainstream candidate like they did in every other presidential election since 1964.