Purely thinking out aloud here. The PL in the early hours of the morning seems very 'precise' - I wonder if there was a PPV event on (Boxing, MMA, something of that nature) ?!?
As for the rest of the day well there was a hell of a lot of sport on - F1, Footy, Rugby - and then there's evening and night time when more people tend to be online.
Not saying any of this is necessarily the cause but it was not uncommon for my TBBQM to look similar to that when I was with Vodafone (VDSL, not 4G). They weren't interested and blamed "local congestion" and the national lockdown.
I've since moved to Idnet and the PL is back where you'd expect it. I.E Next to none at all.