As the tree grows branches point to the same node - meaning we can prune identical nodes and double the probability of landing on that node.
The original tree with 8 steps from beginning to end has 510 nodes versus a mere 230 in the recombined version.
Pruning makes pricing exponentially faster in the face of exponential growth.
Interestingly Firefox sometimes makes ever so small mistakes when calculating the probabilities, leading to less pruning and a slightly less efficient calculation.
The competition is ferocious. Lots of money is being invested into the eco system by Apple, Mozilla, Google and Microsoft. You don't get that with other languages.
How many organisations are pumping money into independent Python or R implementations for example?