What should I say?

So I missed the boat for IB SA 24 I guess, maybe a boutique cold email may land me an interview. BUT…. Big 4 M&A internships have been open several weeks. What on gods earth should I say in my cover letter for Big4 M&A that isn’t “I missed the boat for real IB” like guys, what is big4 m&a looking to hear from its candidates. How can I justify wanting this job, but not come off as “why didn’t this kid jus apply to an IB”

TLDR: Hope this makes sense, have no idea what to write in my cover letter for Big4 M&A given it isn’t what I wanted to do, “why would you want to do M&A for big4 vs Ib for example”