I happened to see about that last 15 minutes, which was perhaps not quite as full of interruptions as was the first part? (Certainly, even at the end, it was clear that Trump was the prime interrupter, refusing to follow the rules regarding a two minute statement that was had been agreed to be without interruption.)
Looking at the comments of the Australian based Trump supporters, it seems an uncontroversial opinion that their dumb ass orange hero interrupted too much and was too aggressive. Many theorised that he wasn't letting Biden hang himself by not allowing him to talk long enough.
I thought that, in the parts I saw, Biden was doing fine in his language, especially if you make allowances for an old issue with stuttering, which I think does still show itself in occasional vocal hesitations.
It is quite unbelievable that some "two sides" commentators think that neither side won because Biden also cut loose with some personal insults. I mean, seriously? Do they think contenders just have to "rise above" the rambling personal aggression of Trump in that context?
The correct view is that Trump's performance could only possibly have appealed to his already rusted on, beyond all reasoning, culture war fighting, base. And anyone who claims they were fence sitting and decided to side with Trump after that performance are, with 99% certainty, not being truthful about there ever being a chance that they were going to vote for Biden.
There is no point in saying that Trump won because he "dominated" and would have impressed his base. His base is not really like rusted on party members of old - they are (in large part) genuine deplorables given permission by their cult leader to finally be open about their worst instincts, and if Trump had gone over and punched Wallace and slapped Biden in the face, they would say they deserved it and still vote for him. He's their projected revenge figure against, basically, a modern world over which they are losing control.
Biden performed well enough to dispel any genuine concern about his mental acuity, and reinforced his basic humanity, serious approach to issues, and genuine move towards at least trying to not further divide Americans and promote self serving conspiracy based theories damaging to confidence in democracy in the way Trump clearly seeks to.
So yeah, obviously, Biden was the winner. It seems most on line polling and the betting market agrees.