In the past these companies have failed because they focused on providing a launch platform. They said, "Build it and they will come". But no one did, so good vehicles died.
But timing is (probably) different now. There are many more launches per year. And not only that, but there's a few paradigm shifts that could help RL out. Small sats are becoming much more common. Electronics got smaller and thus did the satellites. But also, we've been finding that you can use off the shelf electronics if you stay in LEO. Granted, you should use ECC CPUs and memory (but don't have to), but that's a lot cheaper than silicon on sapphire.
This makes things a little different. Before there was little pressure to push down the cost of a launch. If your satellite cost $250m, what's the difference in a few million per launch? And why would you risk that on a newer company? (Why Musk sent up his Tesla) BUT if your satellites are only a few hundred thousand dollars, then there's A LOT of pressure to push down launch costs. You can take more risks on these smaller companies that don't have a good (or any!) track record.
There's a lot more going on too. But I think these small companies have a much better chance of succeeding than their ancestors.