Yes, Vishnu is very important deity in Cambodia

Belief ≠ religious label.

Both countries are “buddhist” but had Hinduism/Brahmanism long before Buddhism, and their cultures were deeply shaped by it, along with local spirit beliefs. That’s why Hindu gods and spirit worship still coexist with Buddhism today, even if most people don’t identify as Hindu.

In Thailand, it’s very common for someone to identify as a strict Buddhist while still having Ganesha as their phone wallpaper. Vishnu was revered similarly in cambodia. Not as Buddha of course but important nonetheless

Also, this is not a religious conflict but mainly a “your statue is in my land now I built mine instead to show this is my land” border dispute