It's not enough to build something that's better. You also need to sneak it in like a Trojan horse into a user's fortress. You can't easily launch a frontal attack on Linux.

One of the most valuable opportunities with mobile is that current technologies can become irrelevant. A big success for L4 is that it made it into mobile phones.

AFAIK a lot of it is due to issues as simple as Linux having more device drivers than Hurd.