I have impression Rishi's plan was to raise the bottom threshold.
That was the plan before today.
But it's so much better to borrow huge amounts of money to give the top 10% £700 more a year, than to give the bottom 10% an extra £700. Gee, I wonder who would be more likely to spend all £700 right away and who might squirrel it away, or spend it on financial advice to avoid paying other tax.