At the time, the argument for Chrome was that Firefox and IE were bloated and their memory requirements were too high.
A system with less than 64 Megabytes of RAM (most computers of the time) would have to lean heavily on spinning rust virtual memory, making everything slow.
However, since then Chrome has become one of the biggest memory hogs that people commonly run.
I don't think lean memory use was the biggest claim Chrome had made. That was the game between IE and Firefox. Google had specifically promoted faster startup times, faster web browsing experience, and tab isolation / sandboxing so a crashing tab wouldn't bring down other tabs with it.
Netscape 6, which was released in 2000 and based on the Mozilla Suite (now SeaMonkey) recommended 64MB of RAM. The Mozilla Suite was the basis of the Phoenix project (later renamed to Firefox) and they shared the same technological underpinnings: Gecko engine, SpiderMonkey JS engine, XUL interface, XPCOM, etc. Phoenix/Firefox was about using the Mozilla technology to deliver just a browser, independent of the suite, with aim of being lighter weight. So while Firefox didn't exist yet its heavier predecessor did.
A system with less than 64 Megabytes of RAM (most computers of the time) would have to lean heavily on spinning rust virtual memory, making everything slow.
However, since then Chrome has become one of the biggest memory hogs that people commonly run.