What explains the decline of agriculture and the rise of cohesion spending?

Explaining EU expenditure policies

There are three interrelated issues concerning EU expenditure policies that need explaining:

Why does the EU tax and spend to the amount that it does in other words, why is the EU budget so small?

Why is the bulk of expenditure in two main areasĀ  agriculture and cohesion policy

What explains the decline of agriculture and the rise of cohesion spending?

Why are some individuals, regions and member states net winners, while others are net losers?