The 2021 Crypto Bull Run: What Investors Learned

The 2021 crypto bull run was driven by pandemic-era easy money, a wave of institutional interest in bitcoin, the explosion of DeFi and NFTs, and huge retail participation — and it ended in the 2022 collapses of Terra, several crypto lenders and FTX. The most important lessons investors learned weren't about which coin to pick but about leverage, custody, hype and taking profits.

Those lessons are relevant to anyone thinking about 2026 and 2027. Market conditions will differ, but human behavior in a boom is remarkably consistent. This guide walks through what happened and what to take from it.

What Drove the 2021 Bull Run

Easy money

In 2020, central banks cut rates to near zero and bought assets on a huge scale, while governments sent stimulus payments. Savers earned almost nothing on cash. That pushed money into risk assets, including crypto. Our article on global liquidity and bitcoin explains the connection.

Institutional and corporate interest

From 2020, publicly listed companies began adding bitcoin to their balance sheets — MicroStrategy (now Strategy) was the most prominent, and Tesla announced a bitcoin purchase in early 2021. Coinbase's listing on Nasdaq in April 2021 brought crypto further into the mainstream. See also: Crypto Market Outlook 2026.

DeFi, NFTs and memecoins

The "DeFi summer" of 2020 popularized lending protocols and decentralized exchanges on Ethereum. In 2021, NFTs exploded into public view, including a digital artwork by Beeple selling at Christie's for tens of millions of dollars. Memecoins such as Dogecoin and Shiba Inu delivered extraordinary rallies driven by social media.

Leverage and yield products

Exchanges offered high leverage, and lenders offered attractive yields on deposits. Many users didn't understand where those yields came from. Related reading: How Long Do Crypto Bull Runs Last?

How It Ended

Bitcoin fell by more than three-quarters from its peak, and many altcoins fell 90% or more. Terra's tokens — now known as Terra Classic — lost almost all their value. Read more in what ended past crypto bull runs.

Lesson 1: Leverage Destroys Long-Term Theses

Many traders were right about crypto's long-term direction but were liquidated in the crashes along the way. Firms that borrowed heavily against crypto collateral failed when prices dropped. If you can't survive a 50% drawdown, your view on the long term doesn't matter. See leverage in a bull run.

Lesson 2: "Not Your Keys, Not Your Coins"

Customers of Celsius, FTX and other platforms found their funds frozen or lost. Platforms that seemed large and safe turned out to be taking hidden risks. Lessons:

• Keep long-term holdings in self-custody you understand, or at least spread funds across platforms.
• Treat high fixed yields as a risk signal, not a feature.
• Check whether platforms publish credible proof of reserves and are regulated where you live.

Our guide on choosing between self-custody and exchange custody covers the trade-offs.

Lesson 3: Yield Always Comes From Somewhere

Terra's Anchor protocol offered high, stable yields on UST deposits. When people asked where the yield came from, the answer turned out to be subsidies and growth that couldn't last. If you can't explain the source of a return, you're likely the source. See algorithmic stablecoins.

Lesson 4: The Fastest Risers Fall Hardest

Memecoins, NFT projects and small-cap tokens rose the most in 2021 and lost the most afterward. Many projects disappeared entirely. Diversifying across dozens of speculative tokens isn't diversification if they all fall together. In a broad crash, correlations between crypto assets tend to rise, so a portfolio of twenty small altcoins can behave like one very risky position.

Lesson 5: Have a Plan to Take Profits

Many investors watched large paper gains evaporate because they never sold anything. Euphoria makes selling feel wrong. Setting profit-taking rules in advance — such as trimming at predefined levels or rebalancing on a schedule — prevents that. Read how to take profits in a crypto bull run without regret.

Lesson 6: Scams Scale With Hype

2021 saw rug pulls, fake NFT mints, phishing sites, impersonation scams and pump-and-dumps flourish. New users with little experience were prime targets. See our guide to bull run scams.

Applying the Lessons to 2026 and 2027

We don't know whether 2026 or 2027 will bring a bull market, a bear market or something in between. But if euphoric conditions return, the same checklist applies:

1. 1Size positions so a 70–90% decline in speculative holdings wouldn't change your life. See sizing your positions.
2. 2Avoid leverage.
3. 3Keep long-term holdings in self-custody or spread across trustworthy, regulated platforms.
4. 4Question every high yield.
5. 5Write down a profit-taking plan before prices rise.
6. 6Verify every token, link and app before using it.

Bottom line

The 2021 bull run showed how far crypto can rise on easy money, new narratives and crowd enthusiasm — and how quickly leverage, opaque platforms and unsustainable yields can turn gains into losses. The next cycle will look different, but the lessons hold: control your risk, custody your assets carefully, take profits on a plan and stay skeptical when everyone else is euphoric.