Upon reflection, did the populist party make wise decision in choosing to support the democratic party’s candidate innthe 1896 presidential election? why or why not?

Yes--third parties don't work in our electoral college system. They would not have gotten any of their goals without a major party. 

Though the Populists joining with the Democrats still don't get them a win in 1896, their ideas become more mainstream. With a big party owning their ideas on the Democratic Platform, they will get more traction. Many of the Populist ideas like an income tax and direct election of senators will happen during the Progressive Era becoming the 16th and 17th amendments.