Although plausible, and part of it, it’s not just that. The second part is much more important (people unwilling to adapt), but one should think about why.

• How sudden & drastic was the change?
• How well trained were people?
• How much support did they get when something went wrong?

That’s the kind of stuff where companies & public administrations usually suck, “change management”.

I’ve seen Germany states jump into open source software strategies to later “regret” them and revert back to their previous state, many times… I hope this time they do it in a more thoughtful way, to avoid giving excuses to closed-source software lobbyists.

• Professional services usually refers to have consultants for contracting. The more the demand for your services, the more people you have to hire to content your clients. Because salaries are usually one of the biggest costs in any company, this kind of business can be a bit more risky when there are economic downfalls and you cannot fire workers quick enough (I’m talking from the perspective of the business owner, leaving ethical aspects aside).
• Subscriptions don’t imply having people personally interacting with the client, because what you offer is not expertise, but a product that can be served to big amounts of clients, independently of how big is your team (of course you end up having to hire more people, but this team growth is much slower).

Their product offers many more features (and more complex ones) than the other services you mentioned. And they also took the time to provide a commercial product, with paid support, integrations…

This is key for companies, as it makes it easier to be productive, plus the SLAs give some peace of mind too.