Almost every cuisine ferments something, and almost none of them ferment it the same way. The variation comes from three inputs that differ by place and that the cook does not choose.
The microbes are local
Traditional fermentation relies on organisms already present on the ingredients, on equipment and in the air of the room where the vessel sits.
Those populations differ by region and even by household, so the same recipe started in two places is inoculated with different communities.
Repeated use of the same vessels and starters concentrates whichever organisms thrive there, which is how a place develops a characteristic result that is difficult to reproduce elsewhere.
The substrate determines what is possible
Fermentation converts what is present, so a starchy grain, a sugary fruit, a protein-rich pulse and a fresh vegetable each offer different raw material.
Starches must first be broken into sugars before most organisms can work on them, which is why grain fermentations often involve an additional enzymatic stage.
Protein-rich substrates produce savoury compounds through the breakdown of amino acids, which is why fermented pulses and fish taste of depth rather than sourness.
Climate sets the pace and the outcome
Warm conditions favour fast-acting organisms and short fermentations, and a batter that is ready overnight in one climate may take two days in another.
Cool conditions slow everything and allow different organisms to compete, which tends to produce longer, more complex fermentations with different flavour compounds.
This is why comparable preparations from hot and cold regions differ in sourness and in aroma even where the ingredients and the method are similar.
Salt is the main control the cook has
Salt concentration selects which organisms can survive, since some tolerate it well and most spoilage organisms do not.
Higher salt slows the process and narrows the range of active organisms, producing a cleaner and more predictable but less complex result.
Lower salt gives faster, livelier fermentation with more risk, which is the trade every traditional method has settled at some particular point.
The purpose differed from place to place
Where the aim was preservation through a long winter, methods favour high salt, low temperature and stability over months.
Where the aim was to make a grain digestible or a batter light, fermentation is short and the product is eaten fresh rather than stored.
Both are the same underlying process solving different problems, which is the clearest reason the results have so little surface resemblance to each other.