I think a lot of the newer available things like the NanoVNA and less of a need for brute force transmitting like the olden days (think FT8) really made a dent in their product line.
Aside from being harder to read in direct sunlight, the NanoVNA is - in my opinion - much a better antenna analyzer than the MFJ analyzers ever were.
There has definitely been a move in the hobby towards computer + store-bought rig (especially for newer hams), which I'm sure didn't help MJFJ's sales. There are also a lot more companies now that MFJ had to compete with for things like tuners (especially auto-tuners), antenna analyzers, digital interfaces, power supplies, etc. Even as late as the early 1990s, MFJ was just about the only game in town (so to speak) for many ham radio accessories.
I'm not surprised that Mr. Jue wants to step away from the company at 80 years of age. And, frankly, I'm not surprised that they did not (try to?) find someone to take the business over. But it is very sad to see them close up shop - will have to stock up on anything I might need before they close up for good.