Softbank is a grossly mismanaged shitshow fueled by an endless money well of Saudi money.
Don't expect it to be behaving rationally.
Of course, given the kind of company that ARM is, any such buyer is going to be, almost by definition, an antitrust situation. So maybe it never could get past regulators. But, from a purely self-interested standpoint, it makes sense for them to try.
I've been avoiding SoftBank because they've got so many other risky ventures, putting money in company at large seems kinda volatile.
Disclamer: long intel, a few thousand shares at $47. not enough to need to pump the stock.
I'm sure a ton of folks would just jump in because everyone would be jumping in.
In this context being private is a huge advantage. Less filings and less shareholders and less publicity gives you a lot more room to manoeuvre.