Yes, I suppose, although of course at one time it had been 100%. Maybe only the strongest lineages survived ? What I really meant, rather than multicellularity

Yes, I suppose, although of course at one time it had been 100%. Maybe only the strongest lineages survived ? What I really meant, rather than multicellularity being invincible, was that it's an obviously beneficial direction, and doesn't seem like it would need any extreme environmental stress to prove beneficial.