If wikipedia is correct, the google acquisition of Android was two years before Palm launched WebOS?
Palm (and RIM) has a kind of first-mover disadvantage; they'd build a fantastic niche, and people loved their devices, but that inherently prevented them from building something completely different like the iPhone which could take the mass market and be "imitated" by Android.
Sure, 2 years before, but in that 2 years period Android looked nothing like iOS. As others have pointed out it was an entirely different kind of UX until Apple announced the iPhone.
WebOS was the first to come along after the iPhone and make something competitive. Android took some time to catch up. I don't think your statement is correct about Palm -- they weren't like RIM, stuck with an old OS for eons unable to switch because legacy; WebOS and Palm Pre were launched pretty soon after the iPhone.
They just didn't do well in the market, because they couldn't keep up on hardware manufacture, and Android took the not-Apple ecosystem over despite being an inferior experience for many years.
Palm (and RIM) has a kind of first-mover disadvantage; they'd build a fantastic niche, and people loved their devices, but that inherently prevented them from building something completely different like the iPhone which could take the mass market and be "imitated" by Android.