They tried to make users happy with Allo, it didn't work, so now they're trying to use their platform leverage. One thing I'm not even really clear on is why Google cares about messaging, but I'm guessing it's more about Android competitiveness than anything else.
They didn't try very hard. I had never heard of Allo until a month ago when I got a Pixel 2 and saw the app pre-installed. If they really wanted to push it, they would have made it the default SMS app.
It seems odd to me that Google has been unable to solve a problem that Apple solved in 2012.