Because the market is forward-looking, and brings all future cashflows to the present.

If it became clear by 2027 that GDP growth would permanently reach 15% (I didn't make that absurdly stupid chart, they did), S&P 500 valuations would immediately 100X or more.

They could take out a credit line against those gains and have unlimited money.

Wait...are you suggesting those predictions might be so unrealistic that its stupid to even publish them? I'm shocked!