I think the key there is the new domain/language.
One of the contractors was a rails dev, the other one was actually just a polyglot, although we had hired him for Ember.js help.
But the project is also a high impact, high stress, and challenging project (COVID vaccination software) so yes the domain, level of challenge, and impact helps tremendously to stand out.
As a tech exec and senior engineer myself, I find it highly appealing to do contract work mainly because there are many options/opportunities, and the ability to take a gap wherever you want. That's why I've had my own company for roughly 12 years.
I do think it'll remain that way for the foreseeable future. Many of the smartest people I know are happy to remain contractors because of the flexibility.
I will say though, that I would never do this without Obamacare (in the US). If not for that, I would be "stuck" in a W-2 job just so I could insure my family. (honestly not trying to pass judgment on people who have 9-5 jobs, I'm just not wired for climbing the corporate ladder, etc)
Which is why I always say, supporting Medicare for All is (ironically) one of the most pro-business moves we could make. It will unleash entrepreneurial spirit unlike anything we've ever seen in the US. The number of 1-2 person businesses will explode. All the talent that's stuck at large employers so they can get those health benefits for their families (even though, thanks to Obamacare, you really don't need to anymore) will get liberated.