Writing my first campaign. I have the major plot points down and could use some opinions.

I'm coming straight from my first campaign I've DMd (Curse of Strahd) and I've decided to write my own campaign for my players. I'm trying to nail down the story at the moment and provide a good hook, interesting villain, etc. Below are my bullet points. Any input on what you feel should be changed or maybe some suggestions based on your own experiences DMing?

Campaign starts in Longsaddle for the Shieldmeet festival. After much merriment, the town is attacked by a cult and the players are forced to watch it burn (Possibly the number of cultists deters the PCs from engaging. This also provides the hook).

The players flee with the rest of the villagers westward, through the forest, to Neverwinter (They are accompanied by a wizard from Silverymoon who was also at the festival). Here (after some sidequests), they're told they may find info on cult south in Waterdeep. The wizard leaves the party and tells them to report to Silverymoon if they find anything and they can all compare notes.

Again, after some side-questing in Waterdeep, they find info on said cult and they head out for Silverymoon. The wizard and the party discuss cult, and decide to try and infiltrate it from the inside. (Details on how they do so aren't worked out yet, Ideas?)

Upon successful infiltration, they stop a ritual in progress and kill the cultists in this area where some resided and they find a tome that is illegibile to the PCs. The wizard says he'll take a look back at Silverymoon and promises to report if he finds anything.

At this point party can do as they wish. After some time they hear word from the wizard and upon meeting him he seems disturbed by what he's read, though he gives only brief info to the party. He tasks them with gathering some ingredients for what he says is a counter-ritual (To stop the summoning of their god, but in reality he's asking for components to make himself into a lich). While the party does not know this, the wizard believes only he can stop what is to come and decides to make himself more powerful. In doing so, he commits atrocities that he knows while bad, are for the greater good.

When the party finally discovers what he's done and what they aided him to do. It's too late, he's turned himself into a lich. (Here is where I'm unsure of what to do next. Maybe he tries to summon this being - which I want to be a Balor - anyway and tries to fight it himself and gets destroyed. Or, maybe he tells the party he will be the protector of these lands -his head filled with delusions of grandeur- and the party can fight him at this time.)

What do you think of this? Suggestions? Comments? Any help would be appreciated.

EDIT: After the feedback, I understand this may have come off as railroady. I will keep this in mind and rethink how I will present this to the players. Thanks for your feedback everyone!