He didn't need an assassination attempt to win, the election was already in his pocket and Biden/Democrats did everything to lose but this last incident carried everything to whole another level. He will use this to fight and clean the corruption which entrenched in every corner of the country. So this is a blessing in disguise for him. Had he died yesterday, it would have triggered a civil war easily and the results of that would be catastrophic. He probably was going to get 60% of the popular votes and now it is more like 80%. It doesn't even make much sense to make a bet on it unless... there is be a second successful murder attempt.
This was going to be a close race, but with this lastest incident Trump has indeed increased his chances to win, the picture of him alone screaming with his fist up to the sky is worth millions in political capital already, it is a truly a blessing in disguise for him, also the fact he quickly mentioned and asked for prayers for the family of those who died, makes him to look even more humane.
I am not sure whether his assassination would have sparked a civil war or not, USA polítics are more complex than that and the average Republican and the establishment would not find convenient for a war to happen in the USA, if anything, Putin would greatly benefit from it happening.
When I have some time, I'll try to find a graph which shows how the odds of Trump changed because of this unpredictable assassination attempt.