While they were running around the floor negotiating during the break, the announcer on Cspan said that they had heard that the Defense team wanted more time to prepare their final arguments. That sounds plausible to me, so maybe that’s why McConnel extended them til Monday.
I am sure it is a negotiated schedule.
I am sure it is in part to avoid Superbowl festivities.
I am sure in part it was to avoid accusations of burying the vote in the weekend.
I am sure in part it was to prevent Tumpy's victory lap at SOTU, saving dems what little face they can..
And to some degree, normal seepage in Senate scheduling.
But I bet you can guess which of the above was more pressing. :D