The weirdness is due to these patents being "continuations", that is, follow-on patents that keep the priority date of the original, but file new claims on the same subject matter. This is usually done to get broader (or sometimes just different) claims than the original. On the flip side, the follow-on patents lifetime is still based on the original filing date.

Also, if there was any prior art that did "basically the same thing" you can bet Samsung would have brought it up. TFA does not give much detail about Samsung's arguments, but only mentions a non-infringement defense.