The Saints had to see Taysom Hill to know.
You can have ideas about what a player will be and the things he can do, but it can only be abstract until something tangible can be evaluated. New Orleans saw that process unfold with Hill this season.
Behind closed doors and during practices, he impressed and built enough confidence and excitement around his performances to garner a two-year deal. Still, you can never know a player until you see his warts, and you need game experience to find out how someone will react in certain situations. With Hill, a fumbling issue got exposed, and perhaps there were some decisions that he would like to have back.