"terribly well"
What would be your standard in treating employees terribly well?
And it is strange to mention Musk and Bezos side by side. Their mode of employment is very different.
In Amazon, you are a preprogrammed cog in a spinning retail machine, micromanaged and followed everywhere by algorithms that seek to squeeze maximal output from you and punish you for slight deviations from the script (such as "not having your hand on a railing if you go upstairs"). They even encourage other workers to report you if you do something frowned upon. Human robots - which corresponds well to the nature of Bezos, who is often described as a way-too-rational, aloof man.
This is not what happens around Musk, who is a very different type of personality. In SpaceX, young engineers do overtime voluntarily because they are working on interesting unsolved problems, precisely the thing that you want to take part in at least once in your life. And it is understood that once they leave for a workplace with less driven culture, their stint at SpaceX will be considered very valuble.
Edit: If you are a youngish creative engineering type, you want to have a go at something that is both difficult and world changing. Most people will never have a chance to do so. So if you really become a part of a team that designs Starship etc., no wonder you will spend hours and hours there.
From my personal experience, chasing a difficult bug in my program means that the day flies by and suddenly, the streetlamps are lit. But the victorious feeling is worth it. And my software products are nothing like Starship.