edit - Looks like Firefox introduced both. But Chrome was incredible in comparison at the time. I recall thinking Firefox was no longer worth it. I made the move back to Firefox a few years ago.
But it was not just niche browsers. By the time of Chrome's debut (2008), just about every browser had tabs—including Internet Explorer:
"With the release of Internet Explorer 7 in 2006, all major web browsers featured a tabbed interface." <https://en.wikipedia.org/wiki/Tab_(interface)#History>
I used to work with a guy who always invoked Firefox in gdb so that when it crashed, he could fix the bug (null ptr deref etc.) and continue. As a “tab hoarder” he would lose a day or two of context and productivity otherwise.
pretty sure opera had tabbed browsing as well.
i just recall chrome being very minimal, clean and fast when it was first released. plus as kreeben said, Google was pretty revered at the time.
Some people apparently think tabs has to be drag-and-droppable, which Opera had in 2003, in order to be called tabs: https://allthatiswrong.wordpress.com/2011/01/14/opera-did-no...
That and better isolation of tabs so that one tab wouldn't ruin your entire browser experience with some javascript that was thrashing.
Tabbed browsing, no idea though.
No one is claiming chrome invented the concept of incognito mode. It was just executed incredibly well.