ZLA Center Controller reported a ground stop at LAS Airport and understaffing at several ATC facilities led to a high workload that caused the sector to be unmanageable and unworkable.

Narrative

When we got in at XA:30 the Controller in Charge (CIC) told us that Traffic Management Unit (TMU) had advised them that LAS would be busy until XD:00; but that's all the info/help we got. The closing coworkers had combined all 5 sectors up before XB:30 and around XB:45. I came back from break and de-combined sectors 54/55 to one scope and my mid partner was working 06/16/34 combined on the other scope. No one could stay to help because they were all already on 10-hour days and off at XA:00. Starting around that time; approximately Day 0 XA:00; I started to get a large number of LAS arrivals on the east side of the complex; while the west side (06/16) was getting spun and put into and out of holding. I had over 25 aircraft landing LAS within a 120-mile radius on 3 different arrival streams; two from ZLC and one from ZDV. TMU told me before they went home that they told ZDV to give us 15 MIT but that was zero help considering the volume I was receiving from all 3 flows. This barrage of arrivals continued on for an hour. There was literally nowhere to put all these aircraft. At one point I turned to my coworker and told him that I was at a loss; I have no idea what to do with all these aircraft there is literally nowhere to put them. My coworker then ended up calling the surrounding centers for me and choosing some aircraft to spin because I didn't have a spare second to go on the line.To add to this complexity; there were bad rides; some minimal weather and still overflights and departure traffic. The frequency congestion was filled with aircraft with lengthy ride reports and questions; aircraft checking in on my frequency in error since the surrounding sectors weren't used to us being de-combined so late; and I had one aircraft requesting a deviation for a buildup. They were getting moderate chop between FL260 and FL360 throughout my sector. The area controller who was working sectors 7/8/35/36 combined (these sectors surround our sectors) was too busy to use CPDLC so I had to 'steal eligibility' on ALL the CPDLC aircraft which added even more tasks to do. This controller was also working both east arrival flows alone.Management was well aware of what was coming and did nothing besides tell the two of us to 'make sure we stay de-combined;' apparently trying to check their box off; they told us not to combine up. Despite staying de-combined; the sector was unmanageable and unworkable. Both my mid partner and I have years of experience at ZLA and neither of us have ever seen something like this; that late at night with no staffing or help.After speaking with coworkers who were on the day shift; there was a ground stop during the day for LAS multiple times; and LAS stayed at a very low arrival rate of 36 all day long and config 1. There were no deviations on the day shift but they were still spun twice despite the low arrival rate. Sounds like the airport was slowed down all day long 'just in case' and then everyone goes home at XB:30 and everyone on the ground takes off at once. What I experienced last night was incredibly dangerous; and I do not say that lightly. If this had happened to two more inexperienced controllers; who knows what the outcome would've been. We are told during these countless safety briefings to just refuse handoffs or spin aircraft when we're overloaded; this is also an illogical response as now we're just pushing off the busy workload on other people. Salt Lake Center had conflict alert going off between multiple of these aircraft as they were trying to spin 4 - 5 of these arrivals for me as well as working their own busy traffic (yesterday was extremely high volume overall). It is completely unacceptable for there to be a ground stop and very low arrival rate all day and then after XB:30 everyone goes home and everyone on the ground takes off at once. It's illogical and dangerous. I want to say that I can't believe this happened; but I can. During safety briefings we're just told to push off aninsane workload on the previous controller who is also busy; when the actual solution should be that all these aircraft should NOT have been in the air AT THE SAME TIME. There were minimal arrivals to LAS after XD:15; why were these 100 aircraft not spread out over the nighttime hours? When I came back to work from XG:00 - XJ:00; I had TWO arrivals to LAS. There is no reason that these air carriers should've all been allowed to depart all at once just to keep their passengers happy. As far as I can tell; absolutely nothing was done to mitigate the situation besides telling me and my coworker we were 'gonna be busy' and then trying to give MIT on one of 7 arrival streams. With staffing already at desperate levels and getting worse and worse with losing people and the terrible new schedule rules; we need something that staggers these arrivals all night. The old way of 'TMU went home; you're all on your own' is NOT going to work anymore and something safety related is going to happen eventually. I know LAS isn't the only airport with this issue; this goes for any airport that's delayed all day and then all delays lifted at XC:00.