It's a different ballgame now though, as self-publishing or creator-owned deals really weren't available to the likes of Siegel, Shuster, Kirby, et. al when they plied their wares in the comic industry. The path to print and to market only went through the big publishers then and they had all the leverage, and had no qualms about using it to take what they wanted form the creators who worked for them for a fraction of their potential worth. The world, and the market has changed since then, and there are work-arounds to reach market that don't go through the corporate comic companies that didn't exist then, and knowing how much regret the likes of Siegel and Kirby expressed about the options available to them later in their lives, one would think they would have taken those work around options rather than sell their babies for a pittance or a regular paycheck. None of them were particularly interested in reverence of fans or legacy, but about maximizing their earning potential and having a path to market for their work. Siegel and Shuster took the path they did because the syndicated newspaper market rejected them, not because they wanted to enrich a fictional universe or contribute to a sandbox. They did so because it was the only way to monetize their work. Had they had other options, they would have taken them, but the only deal available to them was the raw deal they got from National. Kirby was looking for a steady paycheck, and was happy to work for the pay he got, doing the dirty work when things were lean, and he hoped/expected to get a fair share of the credit/reward when times got better, and didn't. Had another option besides staying at Marvel or going to DC been available to him (as it later was with Pacific), he likely would have taken it and done his Fourth World stuff and his other DC and 2nd Marvel term creations on his own terms with his own path to market. But such options didn't present themselves to him until he was in nadir of his career.

Today's creators certainly have choices and opportunities not available to creators of yore, but many who choose to work for and create characters for Marvel/DC these days usually aren't doing so primarily to contribute to someone else's sandbox, even if they grew up fans, it's for far more practical reasons. To make the other creator-owned options viable in the current market, you have to have an established customer base, and that comes form having work on the shelves customers can get access to. Doing work for Marvel and DC is going to make it more likely shop owners will order shelf copies (and not just enough copies to meet preorders) of your books to put them out where more customers can discover them, and creating a new character will usually result in higher preorders, more shelf copies, and more chances of getting product int he hands of end customers who will discover (or rediscover in Liefeld's case) your work and follow you to other projects that you own. It's playing a long game in the market, and using Marvel and DC as a marketing avenue for your work to try to build a large enough customer base for your work to make the creator-owned/non-corporate comic route financially viable.

Liefeld's star has fallen, and he gets the most attention for stuff he did in the 90s (creation of Cable & Deadpool), and he has a new media deal for his Extreme properties, My guess doing MArvel work is a way to put his name back in the spotlight, and creating a new character will make the spotlight brighter with the ensuing hype and marketing, so that he rebuilds some of that name recognition and some of those customer will follow his name to the new Extreme movies and tv shows when they start to debut in the next few years.

Or maybe I am just cynical, but to me, it is the most obvious reason to do something like this for Marvel and DC, a short term sacrifice of ownership on one character for the hope of gaining the long term benefit of audience for all your other characters and properties.

-M

My thinking is that It's nothing character but I thought the same thing about  Deadpool.