I'm afraid Chelsea couldn't start the friendly matches well.

First a draw against Wrexham and now a huge defeat by Celtic, 4-1. Maresca is new around here of course but hopefully he manages to find the right system for the team soon.
Because there isn't a long time period left for the season to start officially. Pochettino was sacked for no reason and now they have to experience the same process again. Enzo Maresca will need to adapt to the team to make things better. The worst case scenario would be his not being able to meet the expectations at all. In that case, I presume that Boehly would regret sacking Pochettino while things were getting better actually.
I'd question why you're taking pre-season friendlies so seriously, but given what gets put in front of Chelsea every week, it's completely understandable
Conceded two goals in 3three minutes in the second half, Chelsea had over 50% possession, 23 shots 10 of which were on target, and scored one penalty. Celtic had 14 shots 11 on target, 47% possession, and scored 4, Imagine if Celtic had their strongest team