Why cook stewing meat low and slow?
If the goal is to melt collagen, couldn't that be done just as easily at a higher temp? 


No, it won't be. 

The reaction which has to happen to the collagen doesn't go quicker when the temperature is higher. You have to get it to 68 Celsius and wait for it to happen. If it is at more than 68 Celsius, it won't happen quicker, or better, or anything. You have no advantages. 

At the same time, if you have a higher temperature, you have more trouble. First, you are wasting a lot of energy to keep the stew hotter over many hours. Second, its liquid can boil off, getting the wrong consistency. Third, if the bottom of the pot becomes too hot, it will burn on. Fourth, anything non-meat in there can suffer from the heat - vegetables can overcook, starch can burn onto the bottom, anything planty (vegetables, herbs, spices) can get its taste destroyed). 

All in all, if you can cook something on a high or a low temperature, choose the low one, it is generally better for everything. Only choose high for foods which have a narrow temperature range which is high.