Justifications for invading aliens in Hard-Scifi setting?

So I'm building out a new storyline in an area of scifi history that I haven't seen explored alot. Pre-FTL but Post-Solar system Colonization.

In my setting, it's 2115, and humans have pretty much dominated the solar system and have split into 2 factions following a brief war 20 or so years ago. The Inner solar system is controlled by Earth with their (teeny) partial Dyson swarm powering everything up to the inner belt*1. The outer solar system is controlled by the colonies on Titan and maybe other Jovian moons who rely on heavy duty fusion reactors supplied by the gas giants atmosphere.

Wide scale asteroid and moon/Mars mining is employed by all human parties. Travel across the solar system is done with Nuclear thermal rockets and military tech is primarily high powered lasers.

The aliens have a technological and capability advantage but nowhere near as severe as your standard 21's century invasion. Population spread across the solar system and the standard KKV (kinetic kill vehicles) can be detected and deflected by lasers.

My point here is that while humanity isn't a peer target it also isn't a soft target.

The aliens have the ability to manipulate gravitons in some fashion, leading to their FTL. Their FTL isn't blindingly fast, only 10-15x light speed. Their offensive and armor tech only has about a 20-30% advantage on ours. Also, relatively small empire, w/ home system extensively colonized, and 2 other star systems in early 1st-3rd colony stage. Only a small number of ships, maybe 20-30, come to the solar system

Realistically, why would these aliens invade the solar system?

Nix a few bad ones

• Resources: no. Way more with way less opposition elsewhere.

-Slaves: Robots are cheaper -Water: see Resources

-Organic Material: pretty easy to build space stations to generate that, especially when FTL takes so long

-Ideology: Feels like a cop-out. Like admitting that you can't come up with a Material reason

Some ideas I've had so far:

-Splinter group or ruthless corporation looking to gain already complete space infrastructure/data for resources and revenge.

-Valuable planetary biosphere much bigger than space station for food/domestic products/organic material generation(biomaterial?)

-Lite Dark Forest eliminating newly discovered competition ahead of time(only became aware of humanity when FTL crossed our radio bubble)

Any other ideas? Preferably ones that dont go against my bad reasons like my current stuff does.

*1:The inner belt is a stream of asteroids deflected into the space between Mars and the earth with hypervelocity impactors (I'll be doing a follow up with anti-FTL tactics, is there a better sub to post that in?)

(Previously posted on r/worldbuilding but they were all way too into the Liu chixan stuff)

I'm currently aiming for a compromise between rouge splinter faction and crossing our radio bubble.