It’s simple.
The mini-budget was bad. It caused the markets to bail out of the UK market, caused Govt borrowing costs to rise, fall, then rise again, accelerated the need to increase interest rates, caused mortgage lenders to withdraw products and bang in higher borrowing costs, and likely increased inflation going forward.
The mini-budget banjaxed what little hope of growth there was left and then kerb stomped the morons who devised it. Reversing the budget was just us running up the white flag to stop the markets doing any more damage. The damage up to that point is already baked in.
It has also damaged UK credibility in the eyes of foreign investors who pine for the days of a politically stable environment where not a lot happens. Four Prime Ministers (five if you include Hunt) in six years is Greek to them.