Jack Dorsey is one of Silicon Valley's eccentrics.

If he was a character in a movie, you'd think he was too cliche.

Acutely earnest and idealistic, he passionately believes that tech can bring about global peace and prosperity.

He's a kind of hippie libertarian, a philosophy that seems somewhat baffling at times. He also happens to be a genuine tech visionary.

His resignation from Twitter is the second time he's left. After leaving the social media giant that he co-founded the first time, he setup the digital payments company Square in 2009 - which has become wildly successful.

He came back to Twitter in 2015.

Until Monday he was running both companies - a situation that didn't sit well with many investors.

Last year Elliott Management, a large Twitter investor, tried to make him choose between the two. They wanted a chief executive that spent their time on Twitter and Twitter alone.

This in part explains why Twitter's share price didn't nose dive when their iconic leader suddenly resigned again.

There has been a prevailing attitude for a long time amongst investors that Twitter is leaving money on the table - that it could generate a lot more revenue from its large and engaged user base.

And certainly a chief executive that had its undivided focus on Twitter might help.

When you compare Twitter to Google or Facebook, it's a relative minnow.

Dorsey has been seen by some as the reason for Twitter's stunted growth. A Twitter purist, who had helped create the platform, but didn't want monetization at the expense of user experience.

To be fair to Dorsey he has tried to experiment with ways to generate more revenue. He also announced a target of 315 million monetizable users by the end of 2023 - and to double revenue in that year.

Twitter has done well at adding users during the pandemic, however that target is hugely ambitious.

It's a goal that incoming chief executive, Parag Agrawal will inherit.

Indian born, Agrawal has risen though the ranks to become an apparently competent and well-respected chief technology officer. He's been described as a safe pair of hands, and he has a huge job ahead of him.

Agrawal instantly takes on Dorsey's monetization headache. Twitter is not Facebook. It holds far less information about you, and therefore the data it holds isn't as valuable to advertisers.

You can also only serve users so many adverts before they start turning away. If your goal is high growth but also revenue increase - that can be a difficult balancing act.

Obsession with cryptocurrencies

Dorsey had become obsessed with cryptocurrencies, and in particular Bitcoin.

He'd recently set up a dedicated crypto team - looking at ways in which the company embraces digital assets and decentralized apps.

The team was to sit under Agrawal - perhaps a sign that digital currencies will play a key role in the new chief executive's vision for the company's growth.

But Twitter has become deeply political in the US, and Agrawal also inherits its moderation problems.

Democrats generally argue that the platform hasn't done enough to take down fake news. They also argue its systems are not good at quickly locating removing hate speech.

Republicans argue that the platform has an anti-conservative bias - demonstrated by the decision to ban Donald Trump after the Capitol Hill riots.

Agrawal has gone from relative obscurity to a major public figure overnight, and will no doubt be called in front of Congress sooner rather than later.

Already, a tweet that he published in 2010 - a quote from the Daily Show - is being used by some Conservatives as evidence that the new chief executive is left-leaning.

Dorsey's goodbye email included a barb at founders who stay too long at the companies they created.

"There's a lot of talk about the importance of a company being 'founder-led'. Ultimately I believe that's severely limiting and a single point of failure," he wrote.

The target of that statement appeared to be Facebook founder Mark Zuckerberg (Elon Musk would agree with Dorsey, having said publicly he doesn't like being Tesla's boss).

But the sentiment has much wider importance. Almost all the eccentric tech founders who created hugely successful companies - Bill Gates, Jeff Bezos, Sergey Brin, Larry Page, Steve Jobs and now Dorsey - have all been replaced with 'safe options'- chief executives that are nothing like their predecessors.

And perhaps Twitter needs that.

As for Dorsey, well he's still young - 45. The last time he had some time away from Twitter he casually built up Square, that's now worth $100bn.

Dorsey can at times be a figure of satire, but he's earned the right to be taken seriously.

BBC