Have any major software company ever created a successful software from the ground up ? No, they all base their work on some language ! They are predatory !
Wait, does any language team ever created a successful implementation from the ground up ? No, they all base their work on some hardware people ! They are predatory !
Wait, does any hardware manufacturers ever created a successful product from the ground up ? No, they all base their work of some software ! They are predatory !
Not even remotely the same situation at all. It's not about using some other existing language/hardware/software and building something on top of it.
Rather, it's a question of cloud vendors repeatedly building open source competing drop-in re-implementations of external db/cache/search products when those original products switch away from FOSS licenses to survive, despite the cloud vendor being a million times larger and better resourced than the original db/cache/search developers. The cloud vendors aren't building something on top of these products (like your examples), but rather they are aiming to competitively replace these products and capture the mindshare of their communities.
This strategy allows the cloud vendor to skip the hard steps of developing a unique product from scratch, designing a client/server protocol from scratch, building a community from scratch, and so many other things.
Separately, the cloud vendors do also build their own unique db/cache/search products, but they just don't ever make them source-available or self-hostable when they do so -- let alone FOSS. That is what makes the pattern of behavior predatory: the big cloud vendors use their dominant positions to bring non-FOSS products to the market, while using FOSS re-implementations to destroy competitors who dare move away from FOSS themselves.
None of the 3 examples you described above are in any way related to this scenario.
Wait, does any language team ever created a successful implementation from the ground up ? No, they all base their work on some hardware people ! They are predatory !
Wait, does any hardware manufacturers ever created a successful product from the ground up ? No, they all base their work of some software ! They are predatory !