Trump spent eight years claiming that the economy under Obama was terrible. This, like almost everything Trump says, is a lie.
Trump has also constantly bragged about how well the stock market is doing since he was installed in the Oval Office. The market has done well, but Trump conveniently ignores the market wave handed to him by Obama. Trump, and his supporters, believe that the market was terrible the day before the election…but amazing the day after.
There are none so blind as those who will not see.