I've come into possession of a dormant social brand and large email database, how can I monetize it?

Kind of depends on who those 120,000 people are, doesn't it?

Ask yourself what they have in common. And ask yourself what it is they want ... or would want if they knew about it.

Then figure out what you can give them that (1) closely matches what they want and (2) can pay you for your time.

Don't look at this as a short-term sales pitch, a single email blast leading to 1 transaction. Rather, look on it as your chance to build up to 120,000 ongoing relationships with new people.

Before you try selling them anything, introduce yourself. Pretend that you're talking to an individual. Present yourself as a brand and as a person. Explain the ownership change. Explain your tentative plans and what you hope to offer them. Ask for feedback. And listen to it. Those who engage are your audience – not the full 120,000, who have mostly moved on by this point, I imagine.

Get to know them before trying to sell them anything.
Since you have a large user base, build cohorts of people (let's say groups of 5k people), and send them a fake personal email related to the brand to:
- do they remember the brand?
- why did they sign up in the first place?
Doing this, you'll be able to better understand their interest.

The idea to split the user base is for you to test several approaches. You'll have to use some analytics tool to track these people (email open, engagement etc...).

We can discuss this further if needed.

Roughly:
Reach out to them saying "it's been a while" and you're just touching base.
Then try to find out what their frustrations are, what they've tried to solve it, why it didn't work, what they would do to get the problem solved, and what one big question they'd want to get answered.
Then build a product around that need and do an internal launch preceded by 3 vids that already give them great value and part of the solutions.
Build an opt-in page and drive the people from the list there.
Host a free webinar.
Then open cart.
then sell your product.
the day before your cart closes, email people from your dorment list, remind them the cart is closing and they can still get the product.
repeat around 3 and 1 hr before closing cart.
Close cart