They were supposed to break into a mine, reclaim a load of valuable incense and return the governor's son from being held captive.

Players aren't "supposed" to do anything, because they have their own will to commit to actions that they want. Nothing cannot be forced on them. You as a DM are there to guide them, and adapt based on what the players do. The players aren't there to follow your story to a T, nor are they there to be restricted by anyone else - within reason.

BIG MISTAKE. Erus, not giving a crap about my carefully planned adventure got the group's approval to tie up the proud ranger and leave him in a cave.

Again... it is not a mistake, because your players cannot be forced into anything. As a DM you need to understand that plans are pretty much almost always going to get foiled. Players are unpredictable, especially new players. The choice to tie up the ranger was a group choice, and they chose that path. As a DM, you need to work with that and adapt to the party choices.

It turned out to be laughable but for my friends first time playing, I felt bad that they went through such an awful adventure.

If they are laughing and having a good time, it was not awful. You have this perception that "It's my game because I'm the DM, and if my players don't do what I want them to, IT'S RUINED!" which is not true in any sense. As a DM, you need to realize that your players happiness is the number 1 priority, even above the priority of you getting what you want as a DM. If the players are happy, you should be happy. It takes some DM's a while to learn this, but once you do, you will have a blast every single game. Player actions that cannot be guessed or perceived ahead of time are the best, because no one would ever expect those hilarious and weird things to happen. Just learn to go with the flow as a DM, and you'll have a blast alongside your players.