How us it that political figures in high office start as medium/high income wage earners and leave as millionaire's?

There's something fishy going on! Pelosi was just a mother of 5 and homemaker when she got into politics. She left her political career as a millionaire - probably from insider trading. People in Congress know what the stocks will be before the public. She tells her husband her secrets and he's the one doing the transactions.
Take the Clintons as well. I remember them saying how poor they were going to be when his term ended. Now they are both millionaire's.
I wonder if Biden is collecting his paycheck for being president? Hummm! Trump was only paid $1.00 and the rest went to charity.
How us it that political figures in high office start as medium/high income wage earners and leave as millionaire's?
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