My take is that a speed upgrade from ISA was desperately needed. There were actually many different standards out there. VLB and Microchannel are some of the more well known ones.
Part of it was also the R&D costs and the potential (and probable) market penetration of whatever standard any particular company would prefer to see gain traction.
VLB was relatively easy and cheap to implement and was a good stop-gap measure until a better product could become available (which was to become PCI, and later (though somewhat unrelated to this discussion here) AGP).
Things went very fast back then. We don't get such changes this fast anymore. 3 years back then was a long time. VLB had served its purpose.
As to whether VLB cards were ever good? The thing is (in my opinion of course) that I've always found contemporary graphics cards of any given usual motherboard to be somewhat lacking. This is why I've always preferred to build systems which would usually havea graphics card that was at least 1 or 2 generations more recent than the motherboard.
With VLB there is so much fewer choices regarding what graphics cards to pick, so whatever board you're gonna pick, you'll probably end up with a graphics card that is barely any more recent compared to the motherboard (noticeable exception being 386 VLB motherboards, or perhaps 486 boards with the oldest/slowest 486 CPUs).
I mean the graphics cards were often the same, with there being both a VLB and a PCI version (and sometimes even ISA). And apart from the standard VLB issues we're left with, having so little choice compared to PCI does make it a rather more poor array of choice when it comes to having good VLB cards for any matching hardware.
Hardware in itself (when looking at how 'fast' any given piece of equipment is) is not fast or slow. it is only when compared to something else (another different part of hardware which it itself is compatible with).