currently FF has comparable devtools, but back in the day, FF was lacking a lot of features, like websocket inspection which was implemented around 2019 [1] where in chrome you could do that since 2011 via net-internals (i'm unable to find the date when it was implemented in devtools). so I think because of thing like these, the popularity of chrome devtools was just getting bigger and bigger.
[1] https://hacks.mozilla.org/2019/10/firefoxs-new-websocket-ins...