Jeb Bush has only one advantage going into Texas, over Ted Cruz - more cash available. So far as name recognition, “Bush” is getting to be an old brand, not that much in prominence in Texas any more, and certainly Ted Cruz has as much or more in that department.
Plus, Senator Cruz resonates more with the Latino population, as they see him as “one of us”, while Jeb is only sort of second-hand “Latino”.
Texas is Cruz Country.