Worldbuilding from the outside in # 5

Documenting a great idea that failed misribily due to ego and stupidity and the bane of D&D 5e.
We had now reached the final phase of the great failed experiment Each player was now going to make a 1st level character to adventure in this world we had created. We were limited to only the races we had created in the previous phase-yet somehow there were races that none of us had put in? We were limited to the classes we created, or so we thought?
So
The races were. Halfling, Human, Alternate Human, Dwarf, Drow, ½ elf, Tabaxi, Gnome and ½ orc. The classes were Monk, Ranger, Paladin, Rogue and Warlock. The characters were a Monk, Two rangers, 2 warlocks and 2 rogues.
At Phase 0 we all agreed we wanted a pretty straight forward game of looking for lost treasure and we all agreed that it was going to be pretty action/combat heavy and to all work together to make characters that could survive in a world with no wizards and no clerics.
Of course after this agreement, which was written down and posted as LAW on the group FB page, only two of us actually followed it!
and as for the actual game, nope it was all about Old Ones and Vampires and Dungeon traps that made no sens and somehow only the MPDG who was boinking the Gm got all the magic and all the special powers. And the GM's brother the monk picked fights with every NPC and most of the PC's and was the worst possibility Murder Hobo!!!!!!!!!!!!!!!!!!!
The game lasted three session before we lost our first player due to frustration and ego conflict with the Murder Hobo. The game lasted two more sessions before the GM moved to another state and proceeded to LOSE HIS FUCKING MIND
that was about it, the rest of sue who actually gave a damn told the Gm to shape the game up or we were out and he folded the game rather then listen, then proceeded to ban us all from his FB while he want off on his crazy tin foil hat insanity
so what went wrong and would this idea actually worked. I am sad because this game cost me two friends and further cemented my idea that 5e players just do not get it.