Bitcoin is struggling again after a brief comeback. Here's what's keeping it down.

• Bitcoin was struggling to hold $70,000 on Monday after last week's chaotic sell-off.
• Other assets like stocks and metals have been recovering, but bitcoin continues to flail.
• Commentators laid out a few reasons for its ongoing struggles on Monday.

Bitcoin bounced off its lows last week, but it's struggling around the $70,000 mark on Monday.

The token's decline brought it to nearly $60,000 last Thursday, before it snapped back on Friday. However, as other assets like stocks and precious metals continue to mount a solid recovery to start the week, bitcoin is in low gear.

The crypto had lost 1% around midday, trading at about $70,100.

As bearish sentiment pressures crypto markets, finance pros have been puzzling over why bitcoin can't shake off the doldrums.

Economist Mohamed El-Erian, chief economic advisor at Allianz, said in an interview on CNBC on Monday that he thinks the current bitcoin meltdown is likely to persist until something changes with the investor base.

"I think the fundamental theme for bitcoin is continued slow institutional adoption, and it's going to be volatile until that base of resident investors, not tourist investors, becomes big enough to absorb it," he said.

"Tourist investors" seems to refer to opportunistic traders with a short-term view of bitcoin, who buy quickly and sell at the first sign of volatility. In El-Erain's view, this has compromised bitcoin's stability as speculative traders have rushed in and out.

"People really bought into adoption that attracted a ton of speculators, and then you got a shakeout," he said, referring to the theme of institutional adoption that helped buoy crypto last year, the largest example of which has been broad participation from spot bitcoin ETFs that hold the token.

Crypto bull Anthony Pompliano told CNBC that a few factors are driving bitcoin's current slump, laying out three reasons he thinks bitcoin is in a rut.

First, the tendency for investors to take profits when bitcoin soars above key thresholds is a headwind, he said, citing selling pressure as the crypto decisively broke above $100,000 last year.

Second, increased financialization of bitcoin is a likely catalyst. Pompliano nodded to the boom in complex trades that allow investors to short, hedge, and generally increase their speculation on bitcoin's price, challenging bitcoin's status as a buy-and-hold investment.

Third, Pompliano argued that the market is pricing in lower inflation, diminishing bitcoin's appeal as "digital gold" and a hedge against rising prices. Also, gold is still supported by central banks, while bitcoin is not.

"When you look at who's buying gold, it's the central banks," he said. "And the central banks are essentially trying to get away from all fiat currency, not just dollars. And so I think that bitcoin is just saying to us, 'hey, look, inflation is not going to be a problem in the next two years.'"