Holy shit!
EDIT TO ADD: This means that a Federal judge believes that evidence of a criminal offence could be found on the premises. From Trump’s announcement of the raid, apparently the search included going into his safe.
This does not necessarily mean Trump himself is the subject of an investigation or potentially facing charges; it could simply be that evidence of someone else’s crime is believed to be findable there.
Whatever this is about, zero chance it would have been carried out without a ton of rigorous work going into being very sure they have sufficient grounds. This is obviously a very significant event; FBI and DOJ will be treading very carefully.
If there is still an ongoing criminal investigation that is at the point of obtaining a search warrant for a former president’s residential estate, someone, assuredly, will be having a no-good very bad day at some point.