Why is my PS5 low in Mbits in the evening?

For whatever reason, my PS5 and PS4 have really few Mbits all the time in the evening, usually I always have 50-70 Mbits but only under 10 Mbits in the evening. (Use LAN cable)

This can be due to various factors.

Perhaps the internet consumption on your street / in your house is higher in the evening, so the bandwidth may be split up depending on the provider, contract and router.
Your router could have set that the router quasi downclocks and reproduces a lower bandwidth.
The Sony Playstation servers are not particularly fast and tend to throttle the bandwidth. Especially in the evening, when a lot of people come home and turn on their consoles, this can overload the server and throttle the bandwidth.