I believe that rio enguaged in buyng high priced assets to make...

I believe that rio enguaged in buyng high priced assets to make it look very expensive for bhp, typically because rio probably believed that those assets would perform sooner than latter.

This is typically what investment bankers call the poison pill. This is when a company engauges in an action that might be a little risky or reduce company value short term to prevent a takeover because of long term upside.
It makes the takeover more difficult. If my anology is correct then this poison pill has done a bit more damage than anticipated lol.

I think manny ppl thought that rio share price was based purely on fundamentals and future upside, but that prediciton was bases on unrealistic commodity prices to some extent. The share price was pumped by institutions, short selling,margin loans and gamblers and here we are in the consequences.