Venkman was hard to use, and mostly focused on the internals of Mozilla. Firebug wasn't just prettier; it was much more usable, and it focused on actual website code. Hence the difference in popularity.
> Firebug wasn't just prettier; it was much more usable
Venkman made some debatable decisions about UI defaults, as is the case with a lot of tools built by old school programmers trying to solve their own problems, but it was more customizable, flexible, and powerful (as is the case with a lot of tools built by old school programmers...). Aside from Firebug's template-based rich console, every feature implemented in Firebug's debug pane was implemented in Venkman, except Venkman gave you even more latitude and control. Firebug's debug pane was a basic UI over a subset of Venkman's APIs, after all, as previously mentioned. It was only many years later (much closer to Firebug's death than its birth) that Firebug got some improvements like showing a variable's value in the source window while stopped at a breakpoint without having to type it into the console (or set a watch on it, or look at its activation record entry). Venkman never had that, but it pales in comparison to all the things that Venkman could do that Firebug did not.
Firebug made its own share of dumb decisions, and the degree of dumb in those instances was higher.
> [Firebug] focused on actual website code
I'm not sure how it could be "focused on actual website code". Venkman was a straightforward JS debugger. (The only way this could possibly make sense is if you're referring to all the stuff baked into Firebug outside it's debug pane—style sheets, live view of document nodes, cookies, and so on; all things outside the purview of a language debugger—in which case it becomes an apples and oranges comparison. It would make more sense to criticize DOM Inspector for any of those things than Venkman. And once again—there were plenty of dumb decisions by Firebug in that comparison is concerned.)
> if you're referring to all the stuff baked into Firebug outside it's debug pane
Yes, you're focusing on the debugger only. The fact is, most people simply did not use Venkman since it was hard to understand how to use it, for what context it was meant. Firebug tied the debugger into a wider context, making it more accessible, and reached a level of popularity that Venkman never had.
