EU delegates and council members have to report their meetings with lobbyists.
Palantir and Thorn lobbyists (just the most famous ones, but you can add another few dozens security and data companies) are recorded meeting many times with countless of them, including Ursula von der Leyen.
It's really as simple as that, sales pitches convincing them of all the benefits of having more intelligence "to catch criminals (wink)".
So, US interests? Which means the NSA?
Even if the NSA was not involved the same data and security companies would have the same incentives imho.
Palantir sells software for analyzing data, like Excel but on a large scale. If "Chat Control" passes, they will need software to analyze the data they collect, which is exactly what Palantir sells. It is just business.
I don't know about Thorn but it looks like the same: they sell software that may be of use for implementing "Chat Control".
But it don't look like it.