Not so overwhelming. The states that Trump one were close. Cruz won the overall delegate count for today because they were close.
As for Cruz winning closed primaries, there is a very good reason for that. Dems are voting in the R primaries because they feel safe that Hillary will win her primary. Instead of wasting their vote, they vote for the R that Hillary is most likely to beat. It happens every presidential election.
Hillary is not worried about Cruz in the least. She’ll blow him out in a landslide.