Max all in a level = replying to questions of an exam in their order
In a nutshell it is stupid.
you should first read all the questions, know how much every one brings and then start replying first to the one you know the best and that brings the most points.
Not making th 8 because your defenses are not up at max is like replying to question 1) and then 2) and then 3) without even reading the following before replying.
You could have added defenses at level 9 at much lower cost than the cost of up what you already have.
Even more silly if you wait to up mines.
2 bow brings much more than max canons and archers towers but cost less.
So up the th to the max you can and then the defense of each th to a cheap level.
Better having 4 anti air at level 3 than 3 at level 4 or even 5 as the up bring only 10 % more while a new defense brings 33 %.
So think before playing.