Hey,
Here's my two cents on this, because I think about it quite a bit. By the way, also keep in mind that they aren't the only magicians to get airtime on television.
All three of these magicians did something radically different than those who preceded them. David Blaine pretty much invented street magic as we know it. Previous to him, "street magic" was what we now call busking. Approaching people on the street, with no table, no big props, and performing close-up magic was pretty much unheard of. At least in the way that he did it. But it's not like he just did this and then got noticed. He took some action to get noticed. He put together a video about his concept of street magic (I recall him saying this video was his way of showing magic by turning the camera on the spectators and not just the magician), and sent it into ABC, where he then landed that first special
Street Magic. So he had an original concept, and he took action by contacting television producers.
Criss Angel was the "hard rock" magician or the "heavy metal" magician. Back in the 90's he had shows that basically combined a rock concert with a magic show. Again, an unheard of concept. He landed bigger a live show in NYC and a little while later, ABC did two television specials with him in the early 2000s. Criss had to knock on a lot of doors, and pitch himself to a lot of people to get to where he is now. I recall him describing that he spent almost eighteen years contacting television producers and owners of big theaters, to only get rejected time after time. Like the guy or not, he worked hard for a long time to get his big break. Eventually he got a meeting with some people at A&E and then that's of course when he landed his television series
Mindfreak. So Criss had an original idea, and the determination to make a name for himself.
As for Dynamo, he also had an original concept. He was the "Hip-hop" magician, and gained notoriety just around the time that Youtube was becoming popular. His street magic videos soon went viral. He combined his skills of cardistry with dance moves, and hip-hop music, which was a new and compelling idea. However it took him quite a long time to get his television show. For about ten years, he continued to get noticed by doing sponsorships with big companies like Adidas, Vitamin Water, and Panasonic. He also performed for his fair share of celebrities, and the internet was a vehicle for him to gain some fame. Eventually he was picked up for his television series
Dynamo: Magician Impossible. So Dynamo had an original concept, and took advantage of the growing popularity of Youtube and the internet.
Now I certainly am not an expert on any of this, and I likely left out a lot of details. But to me it seems that all three of these magicians got on television by having an
idea. An original idea. They also worked hard to get their name out there, probably got a lot of rejection. They contacted and pitched themselves to a lot of people before getting their big break. So I guess the message here is hard work. You can't cut corners, and you certainly have to believe in yourself. These guys had a belief in themselves, and their ideas.
It's not that they had extremely perfect sleights, and proper showmanship. Because frankly, people (not magicians) can rarely tell the difference between a technically simple effect and a knuckle-busting routine that took years to perfect. Like people don't know the difference between Daryl's ambitious card, and Blaine's ambitious card. I mean of course Daryl's routine is incredible, but the concept is the same to a lay audience as Blaine's relatively simple ambitious card. You see what I mean?
I'm going to refer you to this forum that is about pretty much the same thing. It goes into a lot more detail on this subject. Don't be put off by the name, because it's not just another bashing of Criss Angel. Here:
http://forums.ellusionist.com/showthread.php?90099-It-s-Our-Fault-Criss-Angel-Is-Famous
I hope I've provided you some insight on this issue.
-JP