Fan theory Series implied new Vegas canon

Tl;DR i think its a sepperate timeline where the courier didnt exist. Or where his actions didnt matter at all.

Mostly because of the combined state of all factions.

The NCR Overextended and then got their most important base whiped out, implying they couldnt meaningfully conquer hooverdam or the strip. (Wouldnt have happend if the Courier solved all their issues) Else their main Hub wouldnt be shady sans.

The Legion stagnated due to infighting, i think its implied the original Lanius is no more either, likely fell at hooverdam. (A Legion Courier would have resolved Ceasar A or B, Or killed A and B, taking the lead himself).

Leaving Yesman or House.

Now for the house ending. Maybe. But house is dead, his robots too. He had a throw away line about being attacked with a lead pipe (Or a.. 9 iron mayhaps?).

Leaving the Yesman ending. The courier betrayed everybody. Became the king of the strip for a year.. or three? Couldnt hold the upkeep for the securitrons and got pushed out or killed.

which is, if the courier canonically didnt handle the Kingstitle well the easyest slate to start from.. from a writing perspective.

One detail: during the scene where maximus & Xander fight a securitron, the securitron activates battle mode. Which is unlocked in the game by the chip being activated. Implying the courier existed but finally.. didnt matter in the grand sheme of things.