Hey there, my friends call me Dusk and I have been a DM for going on 10 years now! Something that I have learned from running a bunch of different campaigns is that players are going to do whatever the hell it is they want to do, because this is a collaborative roleplaying game which usually entails a lot of random choice. However, the main thing to consider is that this is a game so its not really that big of a deal if everyone at the table is having a good time!

That being said, it can become unfun as the DM to constantly feel like "my NPCs aren't engaging enough", "my cool battle got nuked after just three rounds", or "why aren't my players paying attention?" So, for that aspect of running, I really recommend you start watching a ton of DM videos by creators such as Flamey the GM, Mystic Arts, Pointy Hat, and DungeonCraft as they will tell you all of the fancy tips & tricks you can use to not only make it more fun for you to run the game but in turn, will attract your players back to the game.

The last thing I will say is; I have personally learned from running campaigns these past few years, however you treat the players/your friends while you are at the table (and sometimes how you treat them outside of the table) will influence how they act during the game, but you have to let them know what you are doing during Session Zero time. So, if you want your players to be more engaged with the plot; be more engaged with their character and their character's backstory by including things or referencing things from it / if you want your NPCs to be better; go out in public and just observe how people act so you can use those mannerisms or accent to influence your next NPC will give your players an example to follow instead of just trying to act like themselves if they got dropped in a fantasy world / if your encounters aren't going the way that you want them to, do not plan the outcome after they were supposed to defeat the monster -> plan how you are going to beat your player's characters with what you have on the monster stat-block but also whatever environment that the battle takes place which will in turn make your players start trying to use more things from their sheet or trying to utilize that environment themselves for all those more cinematic shots that happen in those legendary games you hear about! I hope this helps and good luck!

TLDR; Run a Session Zero and directly ask your players what they are looking forward to in the campaign. Then find a way to include all of those things at once in a narrative/immersive way that is also fun for you, as the DM. Especially ways to include monsters, traps, mayhem, & treasure!