7a is almost a flagship, so most people don't have to care their flagship series. Just buy a series. Nowadays "flagship" means that the best camera they can achieve.

Back then, phone providers were competing to be the Nexus brand, so it was generally a loss-leader. The brand that released the Nexus phone would release their actual flagship about 3 months later.

Also, inflation.

They pack a lot more stuff into phones now too. Better screens, multiple cameras, etc. Today's flagships are also just physically larger than the older phones for the differences that makes.

“Now it’s double” is what they will write on the tombstone for this era.