Symptoms of a good thing

Things like remote-working and flexible hours are symptomatic of an industry that is good for workers, but you could stick those perks to an unattractive industry and not change it for the better. So...

Causes

Novelty. Engineering is not new, but the medium is. That's not to say that there are no old ideas holding practitioners back, but there's a lot of forward focus. Computing courses don't have modules on the Michelangelos and Da Vincis of programming, so we move forward, challenging current and old practices.

Possibility. If I were to begin a woodworking, blacksmithing, architectural, or pretty much any other making-things based project right now, I would have to make considerations for budget, materials, tools, and other limiting factors.
With my mid-range computer in front of me, it's more a 'the only limit is your imagination' kind of scenario, with notable exceptions like data science.
I can start my project on GitHub, use a free IDE to program in a free language and all of its free libraries, use some free (or free for the first thousand calls a day) web-services to host a website, keep a database, authenticate requests, and even do some machine learning tasks.

Accessibility. Do you have a computer? With an internet connection? Good enough.
As well as having an open source community with all of the tools you need for a long time, there are blog posts guiding you through getting a website hosted for free in half an hour. There are many websites dedicated to teaching you how to program for free, with some high-quality paid courses for not a lot of money. Stuck on a problem? Ask Stack Overflow.

Intangibility. Like I said, this isn't woodworking, or anything physical (unless you want to work with RaspberryPi or another microprocessor), so the work is wherever you are. Want someone to help from the other side of the world? Timezones are your biggest barrier, big deal. No work in your city? Work remotely.
All of these things are easier said than done, but for many other industries these points are non-starters, or at best a Friday treat.

Sum it up

A new and unique combination of possibility, low barrier to entry, and minimal physical restrictions make for something that is only limited by the people within it, and they're usually willing to help.