I don't think you can determine that they weren't going to make...

I don't think you can determine that they weren't going to make a bid. I wouldn't show my hand in an announcement like this. Should they write "We have bought 20% and would like to pay a 50% premium for the rest"? Furthermore, the original buy was at 34c and bought some up to 39c for a final sell of 36c. So they were either speculating that the price would go higher or they ran out of time to buy the lot.

As far as ESS is concerned, they either think the price will go higher, or they will act faster than they did with WGO.

On another note, if MIN would like to launch a bid, they would always want to flood the market as soon as the announcement came out. Spread some fear, control the price. If expectations run ahead, then any 'premium' offered would've evaporated before any announcement was made.