htc-columbia back in the day was pretty well the top team around when they folded (based on winning sprints with cav, griepel plus some other contributions rather than GC dominance)
BMC with GVA pretty dominant in the classics plus porte as a gc guy, dennis in TTs - survived but only just, after losing most of the top riders
quick step overall dominant in classics, nearly folded, also lost a number of top riders
but none of them have been able to virtually guarantee a TDF win and we know for better or worse that it what counts to most outside of core cycling fans. it is quite a unique situation but i think sponsors like confidence in an outcome. one of cycling's issues is that there is too much risk for sponsors - crashes, poor form/health, drug scandals, heck outside of the WT you're not sure what races your team will even get to ride! with sky you know they will be riding the big races and they have a track record of delivering reliable results. i think that could be worth the higher cost - for many global organisations even sky's budget is minuscule in relation to their marketing budget
as a fan the most interesting thing would be to see the riders distributed around other teams to see how they perform outside of the sky train
will cause chaos on the transfer market if sky do fold, release of that much talent onto the market at the same time is also unprecedented.
one interesting aspect i haven't seen clarified is whether there is any obligation on the team to honour ongoing rider contracts