The article said they had revenue of 100M. Training generally doesn't lead to recurring revenue, so a huge multiplier is not justified. Doesn't seem too cheap to me.
But that's not as "sticky" as software. If you decide to cut costs next year on training because its non-essential, the revenue gets slashed. If I still need to procure stuff, I'm not going to shut off my procurement software to cut costs.
On the flip-side, if cost-cutting becomes important, a company may decide to invest in current employees skills in lieu of hiring new external employees. Any software that isn't mission-critical faces high risk in a cost-cutting environment.
My take on it is that B2B customers are difficult and expensive to acquire and Adecco has a relationship with 100,000 leads. Seems like a good acquisition to me.