"But, if you believe that your company is planning to merge, or...

"But, if you believe that your company is planning to merge, or has secretly
already agreed to merge, and the announcement might not be for several
months, then the resignation of key employees can be seen as bullish.
This is true if you think the employee who resigned would know about the merger,
and might also be redundant in the new company.
When companies merge there are cost savings. Supply chains are merged,
technology is shared, and many employees are let go. You don’t need two chief
financial officers, or two chief medical officers. There will be some redundancy.
These people might have already been informed that their job will be eliminated,
or they might have figured it out by themselves. Not wanting to be unemployed
for any amount of time, they exit prematurely.
If they’re a high-level insider, they probably own stock in the company. Check out
the insider transactions. If they held their stock, but left the company…that can be
a major tell."

Takeovers in a technology/knowledge business involve putting people like Peter and Anil in a set of "Golden Handcuffs" for a period of 2 years so they can transfer their knowledge to the buyer.

Peter is an old guy - retirement time. It happens to most of us, even people like Rupert Murdoch. Don't think too much about it.

In the business I was involved in a takeover of - the CEO announced the takeover offer, waited for the shareholders to approve it, mic dropped and walked. The resignations happen just prior to or after (like days)

BRN isn't going to go through a process like BHP merging with Billiton - where there are synergies to be had by merging the corporate structure and cutting away the redundant capability.