While it's true that viewership declined in the later seasons, it's important to note:
* The creators always intended a finite story: LOST was designed as a six-season arc from the beginning. The final season was a culmination of all the mysteries and character development, and provided a satisfying conclusion for many fans.
* Creative decisions, not ratings: The showrunners chose to end the show after six seasons, even though it could have potentially continued for longer. This decision was driven by their desire to tell a complete and compelling story without being bogged down by ratings pressures or network interference.
* Critical acclaim: While ratings did decline, LOST maintained critical acclaim throughout its run and is widely considered one of the best TV shows ever.
So, while it may appear ABC "cancelled" LOST, it's more accurate to say that the showrunners brought it to a natural end after a fulfilling six-season run.