There's a couple different scenarios, legit or made-up as an excuse:
A) "I thought you were gonna stab me so I moved first. Sorry about that. I know I shouldn't have done that so here's the plan..."
B) "We were uneven in SC and I felt uncomfortable, now we're more even and thus we're all good now, so here's the plan..."
C) "I'm cutting you out of the draw...sorry. But if you want you can help me solo against the people who are encouraging and allowing this here's a plan..."
A rare one I recently tried in a local F2F that actually worked (somewhat; as in I was essential for the pseudo 3/4-way draw on the stalemate line by the end, but that's because I was France which is OP AF):
D) "I'm changing alliances every other year for the lulz, sorry. It was your turn to be stabbed this year, but starting in spring of next year, here's the plan..." [That was my legit reasoning too.
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