This is in fact quite simple:
Longest rest periods (3-5 minutes) are superior for strength and muscle gains
This has been well researched, with multiple studies (legit studies) coming to the same conclusion
Speaking from a historical perspective, long rest periods have been used by powerlifters, strongmen, bodybuilders and olympic lifters
The first well known bodybuilder to break with this general practice was Vince Gironda
He advocated SHORT rest periods, 30-45 seconds
He also advocated short workouts, 45-60 minutes in length
Along with Vince, both Arthur Jones and Mike Mentzer emphasized short or NO rest between exercises
This one reason that HIT workouts are notoriously brief and intense (the other being the very specific tempo)
At the same time these men were advocating their ideas, the aerobics trend became hugely popular in the 70s and 80s
Thus the idea of making lifting more cardiovascular was appealing.
This also dovetailed with exercise science emerging as a field of scientific inquiry
There arose a HORMONAL theory of muscle growth, the theory being that short rest periods would increase Growth hormone and testosterone levels, and this would increase size and strength
This sounds very compelling:
Except its NOT true.
When the theory was finally put to the test, it failed.
Over and over again.
Shorter rest periods were WORSE for muscle growth and strength, not better
This was seen in trained men
https://pubmed.ncbi.nlm.nih.gov/26605807/
It was seen in women as well
https://pubmed.ncbi.nlm.nih.gov/35096249/
The more research was done, the more evidence emerged that short rest periods actually slowed size and strength adaptations
https://pubmed.ncbi.nlm.nih.gov/27126459/
For context, this does not mean that short rest periods “cancel out” your entire workout
Clearly people have trained with short rest periods and gotten results for decades. If you are training and eat enough, you will get a training effect
But its not optimal.
That said, turning a lifting workout in a cardio workout DOES 100% improve cardio
But is that the main effect you want?
If you want size muscle strength and cardio, yes, you can lift weights quickly,
But you’re not getting an optimal result in any one area
