Why Politicians do big scams?

Why do we see politicians when caught in scams and scandals involve big sums? I have found 4 reasons. If you have any you can suggest.

They consider election expense as an investment. Some borrow (from their own species) to finance election expense and some are sponsored by businessman; some spend from their own wallet.

1.      Since election expense is an investment, they must get inflation- and risk-adjusted return.

2.      Further, they have to make money for the coming election.

3.      Once they are involved in illegal practices, this incentivises them to go for big scams and and (Indian) law encourages it. After all, the punishment is same! You plunder 100 crores or 1 crores, the law treats you the (roughly) same. This is the Principle of Equality! What a fucking joke?

4.      Then, when one politician is involved s/he tries to allocate risk. That is, s/he will try to bring others (big politicians and A-Class officers) in the scam.

Next time when you find a politician is caught red-handed think of these reasons mentioned above.

Update:
After watching the Hindi movie "Andolan", i have to add this point also.

In theses times of coalition politics, politicians are unsure  of whether the Coalition government will survive for the next 5 years. So they charge a hefty risk-premium, that is, to engage themleves directly or indirectly in looting the country.