Why did games that require Ps Plus to play multiplayer, not need Ps Plus anymore to go multiplayer?

I remember when i got my first PS4 on Christmas and got Dragon Age: Inquisition, Minecraft, and GTA V. When i was eager to go multiplayer Ps Plus hit me in the face with its pay 2 play bs. So i have been playing free to play games for 8 months, as my mother did not want to get me a subscription. Yesterday i hopped onto Dragon Age: inquisition, i go to multiplayer and it actually worked, no Ps Plus message came up or anything. I did the same for GTA V and it also worked. I haven't tried Uncharted 4 yet. But i really want to know why this happened.

Multiplayer is free as part of the PlayStation Days of Play campaign until 6/16/17. After that you'll have to pay again.

Sony's enabled free access to multiplayer for the week though E3 as part of their Days of Play promotion. That's why it's working for you now, but it'll stop working at the end of the week.