You sound a little confused

Lightning is highly decentralized, i.e. no one controls it

Nonetheless, it has imperfect privacy

Some of its privacy issues come from the popularity of large LSPs like Acinq and Voltage

Popularity and centralization are not the same thing

Centralization entails control but popularity does not

Acinq is popular and has a lot of insight into where many lightning payments come from and go to, because -- due to how popular their routing node is -- they are involved in a lot of those payments

But they do not control their users' funds, so they are not a central point of failure for lightning, i.e. they do not (and cannot) make lightning centralized

If Acinq stopped existing, lightning would continue as normal -- but a lot of people would be sad because they couldn't use Phoenix Wallet and the Acinq routing node anymore