Shalom Daniel,

Thank you for your question. I think the sentence written in the Insights should be clarified. The intention in the Gemara is not that the others are guilty because they did not rise. The Gemara's claim is contrary to what was said immediately before, that the reason they were exempted is because they claim that the bench would have broken in any case after two hours, but they planned to get up after an hour and a half. To this the Gemara answers that the heavy fifth person will respond that since in fact they did not get up immediately, it is difficult to say that they are not related to the breaking of the bench whatsoever, since in the end they all broke the bench together, and there is no significance in the fact that if it had not been for the fifth, the bench would have been broken after two hours and not one hour, since as soon as the fifth sits down, what was up to now becomes irrelevant, and now all five can be considered as they are breaking the bench together after an hour, which is also why they are obligated to get up. It is not because of any Mitzvah towards the fifth person or to the owner of the bench, but because now as soon as there are five people sitting together on a bench that is known to be about to break, the five of them are considered to be breaking the bench together. And even if the fifth is the one who causes the bench to break after an hour (and not after two), since they -- through their sitting -- could also cause the bench to break before the fifth sat down, they are still all considered "Mazikim" along with him.

There is a theoretical idea here to define who the "Mazik" is, and less of a technical matter of who actually broke the bench and at what given moment.

Best Regards,

Aharon Steiner