If you were watching the boards yesterday, you'll likely have noticed the momentous gains posted by Commonwealth Bank of Australia (ASX: CBA) shares.
When the closing bell sounded, shares in the S&P/ASX 200 Index (ASX: XJO) bank stock were up a whopping 6.8% on the day, trading for $169.56 apiece.
This saw Australia's biggest bank stock commanding a market cap of $283.8 billion.
Importantly, the big surge in CBA shares also saw the bank retake its recently lost title of biggest stock on the ASX from Aussie mining giant BHP Group Ltd (ASX: BHP).
BHP shares closed up 1.6% on Wednesday, trading for $51.07 each. This gives BHP a market cap of $259.4 billion.
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BHP's fleeting moment on top
It was only on 27 January that BHP reclaimed the biggest stock crown that it had lost to CBA almost 18 months earlier.
That handover followed on a six-month upward trend in iron ore prices (BHP's number one revenue producer), while copper prices (BHP's number two revenue earner) surged to new records.
At the same time, CBA shares were being pressured with expectations of RBA interest rate cuts in 2026, which could pressure the bank's margins. CommBank stock also came under pressure amid ongoing analyst warnings on the big bank's overvaluation relative to its peers.
But the past three weeks have ushered in a rapid turnaround that's seen BHP lose its biggest stock status far sooner than most market watchers had anticipated.
Part of that turnaround has been driven by slumping iron ore prices, falling from around US$108 per tonne in mid-January to be trading at around US$100 per tonne on Wednesday.
And rather than cutting rates in 2026, resurgent inflation saw the RBA increase the official interest rate to 3.85% last Tuesday, which could help CBA's margins.
At the end of it all, BHP shares gained 2.7% since 27 January through to yesterday's market close, while CBA shares have rocketed 13% over this same time.
And so the old king is back. For how long, remains to be seen.
Why did CBA shares go gangbusters on Wednesday?
The outsized gains posted by CBA shares on Wednesday followed the release of the bank's unexpectedly strong half-year results.
Highlights included a 6% year-on-year increase in cash net profits after tax (NPAT) to $5.45 billion.
With profits soaring, CBA rewarded stockholders with a fully-franked interim dividend of $2.35 per share, up 4% from last year's interim dividend payout.
