Because people would have learned that when "before" is used before a part that has "was", it should follow the form "before x was x, x was y".

Such a form was created via generalising similar sentences to reduce neuron usage since redundancy will get reduced.

So the sentences "before Facebook was Meta, Facebook was Facebook" and "before Google was Alphabet, Google was Google" can be generalised to just "Google", "Alphabet" pair and "Facebook", "Meta" pair, reducing 3 neurons cost for the second sentence since "before x was x, x was y" can be used for it.

The pairs can also be used for other forms such as "x was y in the past" and so also allows the pairs to be used for other forms despite never hearing the pair being used in such a form.