Correlation is not causation, that Trump is not over 50% at this time can show equally as well that republican voters are careful critical thinkers, letting the process play out for the best candidate.
The other way to look at it is a non-sitting presidential candidate has the largest primary support ever seen leading up to the primaries.
Why should your opinion be any more valid than the one I just made up explaining trumps primary support?
It’s not my opinion that in poll after poll 50% of Republican voters support another candidate.