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Technology changes, the market changes, the economics change, and software tools need to change along with them.

In the end, decisions have to make sense from a business perspective so you have to balance hardware costs with development costs and time to market. As more and more computing devices have come into use in more and more places, the number of niches which need to balance those factors in different ways has also increased. The result has been newer languages which fit those application niches better.

There has also been a general trend away from the proprietary languages or language dialects of a few decades ago to open source languages. I'm sure you remember for example the proprietary 4GL languages which were supposed to, if you believed the salesmen, take over the market, but which faded from the scene along with the companies that owned them. The proprietary languages have been nearly entirely replaced by open source alternatives as the latter have nearly frictionless adoption paths which lead directly to the people who use them.