LIBOR was developed in '86. The LIBOR scandal broke in 2012, with evidence of bad conduct going back to '08 or so. The LIBOR to SOFR transition was officially kicked off around 2016. Due to the complexity, the transition took 5 years.

The LIBOR rate-setting mechanism was a reasonable design for the world of 1986 [1], when finance was a smaller club and trust among bankers was higher. Also, it wasn't clear back then that the volume of contracts referencing LIBOR would grow to become many trillions of dollars just a short couple decades later.

When problems finally became very clear, we replaced it.

[1] One criticism often levied at LIBOR is why it sufficed to take a windsorized bank poll instead of looking at something more reliable, such as market transactions. But that's ahistoric: in 1986, banks didn't always do unsecured 3m lending on a daily basis. And later on, banks mostly stopped doing unsecured lending to one another entirely. So critics who suggest that LIBOR should've looked at market transactions entirely miss that finance, actually practiced, is a constantly moving target and it's hard to predict the future when designing benchmarks. SOFR, LIBOR's replacement, looks at secured interbank lending — a practice that was rare when LIBOR was created.