One thing to keep in mind, with something like this, employees' stock is almost certainly worth $0. There will likely be some sort of retention plan for some set of employees, but their stock in GA probably won't be worth anything. The founders will likely have some sort of bonus, and the investors will make some money (not home-run money, but money). I guess they deserve a congrats, but to me it's worth remembering that most likely employees, who viewed their stock options as a part of their compensation, will be left with nothing but a thank you.
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.