AFAIK, when they were all made to compete against each other in MMA it quickly became obvious that Brazilian jiu-jitsu was top dog.
Not really. BJJ was very successful in the early days of what we now call MMA because everyone was playing a new sport with new rules and those rules allowed new tactics that were unfamiliar. BJJ's style of ground fighting was alien to practitioners of many other styles and they hadn't trained to defend against it, but also crucially, within the rules of MMA taking your opponent to the ground is something you can often achieve and with relative safety, so BJJers initially enjoyed a big natural advantage by being able to move the fight to their territory. Fighters from other styles quickly learned to sprawl, posture up on the ground, and so on, after which BJJ still offered effective techniques but wasn't nearly as dominant as it had been in the early days.
The analogy is quite flawed anyway, though. MMA is a great sport for those who enjoy it, but it's still a sport and still has its own rules. What works in the octagon, with a fence around the outside and a clean, flat floor, between exactly two fighters wearing fight-friendly clothing, when both are unarmed and neither is allowed to employ "dirty fighting" techniques is... well, not necessarily what would work without those rules, whether in a different sport or in any sort of real life altercation.
Not really. BJJ was very successful in the early days of what we now call MMA because everyone was playing a new sport with new rules and those rules allowed new tactics that were unfamiliar. BJJ's style of ground fighting was alien to practitioners of many other styles and they hadn't trained to defend against it, but also crucially, within the rules of MMA taking your opponent to the ground is something you can often achieve and with relative safety, so BJJers initially enjoyed a big natural advantage by being able to move the fight to their territory. Fighters from other styles quickly learned to sprawl, posture up on the ground, and so on, after which BJJ still offered effective techniques but wasn't nearly as dominant as it had been in the early days.
The analogy is quite flawed anyway, though. MMA is a great sport for those who enjoy it, but it's still a sport and still has its own rules. What works in the octagon, with a fence around the outside and a clean, flat floor, between exactly two fighters wearing fight-friendly clothing, when both are unarmed and neither is allowed to employ "dirty fighting" techniques is... well, not necessarily what would work without those rules, whether in a different sport or in any sort of real life altercation.