There are a lot of hispanics in Texas and they are overwhelmingly against Trump.
In the past, the percentage of their members voting were very low, but there's been a lot of movement in the national hispanic community to register to vote this year.
It stands to reason that by registering to vote, they are going to vote... and it won't be for Trump.
Whether that's enough to flip Texas? November will tell. But I'd be worried about this, as once a person starts voting, they tend to continue voting.