State Farm attributed the decision to three factors: "historic increases in construction costs outpacing inflation, rapidly growing catastrophe exposure, and a challenging reinsurance market." Reinsurance is a method of transferring some of an insurer's risk to other insurers.
Existing policies will stay in effect -- for now. There's always the possibility that, if things keep deteriorating, State Farm could decide to "non-renew" current policy-holders. That's what AIG did last year, sending thousands of high-end homeowners scrambling to find new coverage.
The announcement's timing -- on a Friday afternoon heading into a long holiday weekend -- seemed intended to minimize publicity. In statement, State Farm said it "will cease accepting new applications including all business and personal lines property and casualty insurance, effective May 27, 2023. This decision does not impact personal auto insurance." The halt seems to include renters insurance, though the announcement wasn't explicit on that count.