My manager quit on a Tuesday and I got her job by Friday, then everything went sideways
Three people above me left in one week at my Denver office, so I raised my hand for the lead role even though I had 10 months on the job. I said yes to a $68k salary bump without asking what the team actually looked like, and 4 of the 6 people I'd be managing had more time at the company than me. If your boss walks out and they offer you the seat fast, what questions would you ask before saying yes?
The "everything went sideways" part sounds like it was gonna happen no matter what you asked, honestly. You had 10 months and four people under you with more time in the building, that's just a rough spot to land in.