That was explicitly a thing WotC was saying, that the volume of lore and existing detail was a deterrent to new players getting into the Forgotten Realms and for DMs to choose to run the setting. A 100 year time advancement, a world shakeup, and a three big RPG books and done publishing plan for the setting (player's book, DM setting guide, and a big module), meant it was easy to get into.
Not everyone can be Eric Boyd.
That had been a thing already.
1e had its big boxed set campaign setting, and a series of regional sourcebooks, 2e redid the core with the slim
Forgotten Realms Adventures hardcover then the
2e Forgotten Realms Campaign Setting big boxed set then a bunch of sourcebooks and regional boxed sets (covering new areas and redoing old ones) then the later 2e
Player's Guide to the Forgotten Realms intended an easier intro into again the core setting, then 3e had its own huge hardcover
Forgotten Realms Campaign Setting book and a series of regional sourcebooks.
4e was notable for its comparative disciplined restraint here, just the three books and no regional sourcebooks, just dragon articles which were part of the online subscription. Plus with the timeline advancement and world changes it was a much bigger proportion of completely new stuff compared to 2e and 3e.
Tieflings were there pre-4e, warlocks and warlords were easy to incorporate. Dragonborn there was no pretending they were always there, the world changing event in the time advance explicitly brought them in so they were now established in the time advanced 4e FR.