To be fair, that's because "adblock" basically defined the space. They are entitled to the name recognition, since they built it themselves. It's a bit like WinZip vs 7-Zip.
Good hypothesis, but I suspect it is because of the search algorithm matching words
Yes, but "adblock" wasn't a word before AdBlock appeared, that's my point.
However, "adblock" was a word before "AdBlock Plus" appeared.