In this case it was easy to see. The economic crisis before had seen a more layoffs. So companies knew the effect and they wanted to avoid it. They wanted to keep their workforce to avoid the cost of rehiring well trained people, to be able to take advantage from the recovery as early as possible, etc.
It was not just the Unions. Even the conservative government also was part of it.
Never said "just the unions". But remember the VW deal in the 90s about the 4 day workweek, to avoid layoffs as VW cut down production back then? That was the unions, and that was a milestone to show how it could be done. So when this crisis came, there was some good experience with temporarily reduced work hours.
In this case it was easy to see. The economic crisis before had seen a more layoffs. So companies knew the effect and they wanted to avoid it. They wanted to keep their workforce to avoid the cost of rehiring well trained people, to be able to take advantage from the recovery as early as possible, etc.
It was not just the Unions. Even the conservative government also was part of it.