This answers your question by suggesting some avenues of further research. This is one of those cases where just knowing the right buzzwords helps with the search.
You could start by doing some research on Fernando Corbato and the Compatible Time Sharing System (CTSS) for the IBM 7090/7094. This was one of the pioneering projects in timesharing. You could follow up with Multics, and maybe even unix, although unix was initially not built for multiple concurrent users.
Also look into Digital Equipment Corporation (DEC) and Bolt, Beranek, and Newman (BBN). Also Scientific Data Systems (SDS) which was bought out by Xerox, and the Xerox Palo Alto Research Center (PARC). PARC was more geared towards servers in a local area network, where each user has a personal computer on the desk.
Early DEC machines like the PDP-1 were adapted for timesharing, and the PDP-6 was specifically organized to run a timeshared operating system. The PDP-10, a successor to the PDP-6, was a major player in the timesharing vendor field in the early 1970s. You might look up the corporate history of Compuserve, as an example of a timesharing service bureau. The VAX, a successor to the PDP-11, was a scalable timesharing system, and was DEC's flagship product through the 1980s. VMS was the culmination of a lot of evolution in timesharing operating systems.
Eventually, the minicomputer and the microcomputer eroded the market for timesharing systems. Cloud computing did not take off until communications progressed to where broadband was cheap and ubiquitous.
As far as hacking is concerned, you might want to start with Hackers: Heroes of the Computer Revolution. This book deals with the history of hacking, which intersects with the history of timesharing.
This is only a partial answer, as your question is very broad.