That's because they were terrible and useless. When I was at MSFT in 2005, I was given a Toshiba convertible laptop (two of them actually) that turned into a tablet for no apparent reason whatsoever. It served no actual purpose that I could discern. I hated that machine more than I've hated any other device I've used. Apple did not just make tablets pretty - they made tablets actually functional and useful.
It's abundantly clear that Apple 'made' the tablet space. Everything before then was beyond terrible.
Now as far as their litigation goes, Apple is very good at getting patents for things. It's part of their business model to patent everything they do and aggressively go after anyone who violates those patents. You can disagree with the method, but it's obviously quite successful.
To be clear, Apple aren't the only ones. Most technology companies in the SV do the exact same thing.
I agree, Apple made the consumer tablet space. Prior to that it was pretty much field service and medical applications (hence why there are so many examples of rugged TabletPCs). Microsoft has pretty much failed in UI design for quite some time (though, I think Windows 8 is a turn around for tablets). Now that I think about it, there were quite a few tech pundits at the time that thought the iPad was going to be a failure like the Newton.
Everyone is good at getting patents right now because the USPTO doesn't do more than a basic 'is there already a patent for this' check before issuing the patent. The EFF recently had a good article on why software patents shouldn't exist
. I tend to agree with them, at the very least the length of a software patent should be very
short, no longer than 3-4 years. There's also no requirement that you do anything but hold the patents. Implementing a system where the patent has to be actively used within a certain timeframe would cut down on the patent trolling problem. For example, you should get a 1 or 2 year initial patent where you don't have to use it. After that if you can show that you're using the patent, you can renew it for an additional year or two.
Edit: Just to add more fuel on the fire: Google wins a slide-to-unlock patent of their own.