That's why this is an investigation looking for evidence and not a conviction.

This is how it works, at least in civil law countries. If the prosecutor has reasonable suspicious that a crime is taking place they send the so-called "judiciary police" to gather evidence. If they find none (or they're inconclusive etc...) the charges are dropped, otherwise they ask the court to go to trial.

On some occasions I take on judiciary police duties for animal welfare. Just last week I participated in a raid. We were not there to arrest anyone, just to gather evidence so the prosecutor could decide whether to press charges and go to trial.

Note that the raid itself is a punishment. It's normal for them to seize all electronic devices. How is X France supposed to do any business without any electronic devices? And even when charges are dropped, the devices are never returned.