You want to prepare the jello first. Then pour over crushed fruit. Otherwise the filling will melt and not firm up. Then chill until it is set.

Paula stated in the video she does not drain the pineapple.

You do not need to coat the pan with cooking spray. The pretzels were mixed with 1-1/2 sticks of butter, so that would be more than sufficient for the pretzel mixture not to stick.

Paula said she did not drain the pineapple.

Were the pretzels crushed finely? The "crust" works similarly to how a graham cracker crust does, so making sure it's fine, so that all the pieces can absorb the butter and stick together is important. And letting it cool is also important before adding the filling. Lastly, if it was made too far in advance, it may have gotten soggy from the gelatin and fruit..