The top 5% are part of the top quintile. You are treating the entry point as the limit, it's not. The mean income of that quintile was over 250K. That group represents the TOP 20% of all earners, and you want to give them a tax cut.
And everyone can still itemize, it's just that the cap affects the higher income earners harder. The upper middle class can still take a $10K SALT deduction, and a MID up to 750K.
If you have a million-dollar mortgage, you are well above a middle-class threshold.
Maybe it touched a few at the very upper end of the scale, but it hit the very wealthy much harder, because the deduction was a much higher percentage of their after-tax income by comparison.
What actually happened is a lot fewer middle-income people had to itemize, because doubling the standard deduction made it no longer beneficial. That also saves them money on tax preparation.
If the law is allowed to expire, everyone at the bottom of the scale will get a big tax hike for 2025. The child tax credit will be halved, the standard deduction will be halved, small businesses will lose the QBI deduction and bonus depreciation.
Only the wealthy will benefit when the SALT and MID caps are lifted.