I suspect most glider pilots are awaiting the accident investigation report, rather than speculating.
On the wider issue of structural strength, it's worth noting that most gliders are far stronger (for their size) than either GA or commercial aircraft. The 1967 design glass fibre Open Cirrus was tested by the German LBA which failed to break the wings at 15g positive (I notice the weight every time I assemble mine!). More recent glass fibre gliders are less over-built, but still have g-limits well above normal GA aircraft - I checked out one current model and find limits of +7.2g/-3.6g. This is not a special aerobatic glider, just a normal "U" class type.
As a regular reader of accident reports (hoping to learn how to avoid them), my impression is that I have only seen two causes of structural failure:
1. Failure of airframe components as a result of poor storage (wood), corrosion (metal) or poor repair.
2. Failure of wing/tailplane caused by (usually unintentional) flight outside the design envelope.
From the limited information, this looks like (2). If a glider is flying at or near VNE, and the flap setting changes suddenly or airbrakes come open, the resulting change in loads might be sufficient to damage the airframe. The same would be true of any aircraft. However, we won't know until we read the accident report.
Anyone flying in a glider for the first time will never be flying that close to the edge of the envelope, nor indeed until they are an experienced pilot and decide to push to the limits (or forget their training and allow the aircraft to do this on its own, e.g. in a spiral dive).
I take people on introductory gliding lessons, and we typically fly at 1/3 VNE and do no unusual attitude flying. The primary risks, like all flying, are midairs and botched landings. Our training aims to avoid both.