The left has never been in power and the left never has the backing of the billionaires.
The far right can grow because huge sums of money are being invested into them, with the expectation that the rich will benefit.
If the left got power they would go after billionaires and as such all efforts are made to discredit them and ensure they cannot get power.
You cannot reform the system and save it. It will simply do the same thing where the rich amass power and influence to undo the reforms over time as people get complacent. The only real solution is revolution.