Everyone agrees EC261 applies. The issue is that LX and Switzerland more generally don’t follow the ECJ jurisprudence on the regulation. So unless there is an EU angle involved the strict interpretation applies. In this case that means that all the ECJ jurisprudence about extraordinary circumstances vs what reasonably can be foreseen does not play a role.

OP will have to make a case that this was travel to an EU country via Switzerland, not to (a stop over of >24h) to Switzerland. If an UK court rejects this argument, (s)he has little recourse.