“What’s there to be happy about? Job’s not finished.”

It was a response that exemplified what later became known as the “Mamba mentality”—a mindset of ruthless dedication to one’s goals. Until recently, Federal Reserve Chair Jerome Powell was sporting a similarly “relentless” Mamba-like focus towards fighting inflation, according to Jason Draho, head of asset allocation and chief investment officer for the Americas at UBS. 

At the central bank’s annual symposium in Jackson Hole, Wyo., in August, for example, Powell said that he would raise interest rates to restore price stability even if it meant “some pain” for households and businesses. The comments swiftly ended a summer stock rally, and since then the Fed chair has maintained a consistent inflation-focused stance. 

But at the Federal Open Market Committee (FOMC) press conference this week, after raising interest rates by the expected 25 basis points, Powell struck a very different tone that led the S&P 500 to rise nearly 2.5% in the past two days.

“We can now say, I think for the first time, that the disinflationary process has started,” he told reporters, arguing that the U.S. economy will likely avoid a recession in 2023 as consumer price increases slow.

Draho said that Powell’s comments “weren’t consistent” with the Mamba mentality he showed in previous press conferences. 

“If Powell was channeling his inner Kobe during his Jackson Hole speech, which was short, clear, and unambiguous that the Fed will do what’s necessary to bring down inflation, the same wasn’t true yesterday,” he wrote in a Thursday research note. “Far from putting an end to market momentum….yesterday’s FOMC outcome is more likely to exacerbate it for the time being.”

Diane Swonk, chief economist at the tax advisory firm KPMG, said in a Thursday tweet that she worries stocks’ rise could exacerbate inflation, forcing Powell to do “a lot of backtracking” or even hike interest rates more than expected in coming months.

Before the FOMC meeting this week, investors were worried that Powell was so dedicated to bringing inflation down to his 2% target that he would end up causing an “otherwise avoidable and unnecessary recession,” according to Draho.

“You wouldn’t have gotten that impression from Powell’s press conference [this week],” he noted. “Which explains why equities rallied and Treasury yields fell as it was happening.”

But Draho warned that the interpretation of Powell’s tone as being optimistic will “heighten” FOMO—or the fear of missing out—and lead investors to buy stocks at a time when the “risk-reward tradeoff” is “less attractive.”

Many top Wall Street strategists have argued in recent weeks that corporate earnings are still deteriorating, and because the Fed has no plans to cut rates this year, 2022’s bear market could return with a vengeance.

“Once people realize the Fed’s not cutting rates—there’s no more heroin, so to speak—then we’re going to price the fundamentals, which are clearly deteriorating in our view,” Morgan Stanley’s chief investment officer and chief U.S. equity strategist, Mike Wilson, told CNBC Tuesday.