I think it was about durability. Brogdan has missed significant time due to injury. It made them nervous to depend on him I think.
75
48
and 65 are his games played in his first 3 years. Not great.
His playoff averages are
13/3.4/4.9 pts/ast/reb
It's ok, but the advanced numbers aren't good in the playoffs at all. His great % on 2's 3's and ft's went down to roleplayer level.
Bledsoe in the playoffs
13.7/4.3/3.7
They may have looked at the numbers and decided it was a wash. I think if you look at the numbers and say do we want Bledsoe for 17M or Brogdan whose numbers really aren't that different in the playoffs at 21.25M, you could convince yourself. That is just looking at the statsheet though.
Since this season started it is a lot harder to reconcile.
The big issue to me is the 3pt shooting. Bledsoe just isn't good there, and Brogdan is, even if he shot 36% in the playoffs. Probably worth the 4M per year for a guy that plays so many minutes.