@ancientgran
Part of the point of furlough was to ensure that businesses survived and were therefore around at the end of lockdown to provide viable employment. Let's say there was no furlough and you run a hotel. Your reception staff, chef, housekeeping, waitressing staff etc. all become redundant when hotels are shut. You can't afford to pay them for an indefinite period of time with no money coming in. As the hotel owner, you would have to pay redundancy pay unless the government subsidised this or allowed you not to pay it. This in itself may make you insolvent, particularly when combined with having to refund customers etc..
Your staff go onto job seekers and probably try to find other jobs (some will probably be successful but some won't be).
At that point a large part of your business has been destroyed - you don't have any staff so can't reopen easily even when restrictions are eased and certainly not on a few days notice.
If you still want to run a hotel business, you would wait until you were absolutely sure hotels could reopen long-term and be profitable because you don't want to find a whole new staff team, train them and then have to make them all redundant again. You are very unlikely to be able to hire exactly the same team back because people are going to have found new employment where they can or decided they don't want to work for you any more.
You may well decide, in that position, to sell off your hotel to be converted into housing. All the jobs in that hotel are then lost.
If you work through that scenario with other businesses across the economy as a whole, you can see how no furlough would have led to millions of job losses.
There may have been a different way to set up the scheme which would have worked better or been less expensive but I think it was one of the things we got right overall.