Caveat: I still feel like a noob after doing this for about a year, so there may be others who will have better/more complete answers than I.
There are a few different configurations, and what you want depends on which configuration.
Many in → many out (this sounds like what you are describing)
If you have different videos you want to play on the screens (as in video A plays on screen A, video B on screen B), then a matrix switcher could work. There are HD matrix switchers out there, but I’ve only played around with SD (composite) ones. Matrix switchers tend to come in multiples of 8. An 8x8 matrix switcher will have 8 inputs and 8 outputs and you can configure it where input 1 goes to outputs 1,3,5 and input 2 goes to inputs 2,4,6, or any permutation with the limit of one input into each output (will not combine or mix multiple inputs into the same output). I have also seen 16x16 and 32x32, but 8x8 is more common. Kramer and Extron are two common manufacturers of these products, at least in the retro SD versions that I shop for. There is likely some kind of limit of how many distinct outputs you can get out of whatever computer you are using, but each video will need to be on its own cable for a matrix switcher to work for this setup.
One input > Multiple outputs
For this, look for a “distribution amplifier” there is some discussion of (SD) ones in this thread Video amplifier - #7 by pixelflowers other terms I have seen are “video splitter”
One input cut into blocks so that multiple monitors that are next to each other make up a video wall (i.e. the top left corner of the source video is displayed on the top left monitor etc.)
There are probably high-end devices to do this for HD, but there was also a “Pi Wall” project to do this with Raspberry Pis, however it hasn’t been kept up to date with the Pi 4, and it’s hard to obtain enough Pis of the model needed to run it. More discussion of that concept in this thread Different options for contious CRT video wall - #10 by jotta_rs.