This is unremarkable. Companies use contract labour for the express reason that they can dip in and dip out. Sounds like Appen were on a gravy train and didn't work hard enough to diversify their portfolio of clients.
Reminds me of that episode of Mad Men where Lucky Strike drops SCDP as their advertising agency. Hope they have their Don Draper
I agree, it looks like they will be back at the numbers from 2019. Which is of course a stepback, but I imagine they will learn something from it. Overall they are still growing, for example, in 2015 they had "only" $43.83 Mil in revenue.