Shorter focal length lenses are easier/cheaper to make. The Entrance pupil (or Objective lens diameter) in the above examples are just 5mm, 17.85mm, and 9.6mm respectively. A long focal length with fast f-ratio, even if the lens' output image circle size does not need to be large (just large enough to cover videocam's tiny type-1/2" sensor area), the price will be high and Chromatic Aberration will require premium optics.
What you are describing is known as the common imaging triads:
(a) make the exposure time longer, thus more photons can be collected
(b) make the optical system more efficient to "funnel" the incoming photon flux to the "photon detection apparatus". E.g., fast optics, better lens coating (if refractors, if typical camera lenses), better mirror coating (if reflectors).
© make the "photon detection apparatus" (e.g., an image sensor) more efficient in converting/processing/displaying an image.
For (a), requires better tracking, polar alignment, good light pollution control, and better seeing.
For (b), requires more investment on premium optics
For ©, requires more technology advancements (opto-electronics, electronics, image science & processing, etc.) and sometimes serious money.
In another word, under photon starvation shooting condition (like us the astro people), that Niagara River is just a drying stream and would require a lot of help, (a)+(b)+© incurs a lot of trade-offs.
Luckily, in this VEAA branch, at the current time, I'd say it's a golden age under these constraints:
- inexpensive long exposure videocams (re-purposed from mass-market security-industry day-night CCTV cameras) are readily available
- its low spatial resolution, (arguably some may add the word barely) good enough (NTSC video) quality, and tiny sensor area put less burdens on mount's tracking and premium optics
From this baseline, there are multiple directions to branch out. Some will say the ROI (return of investment) will not be that great any more
. Of course everyone is entitled to have his/her own opinions on those factors.