Mark Zuckerberg somberly entered the Brussels European Parliament building on Tuesday night, and left less than two hours later beaming. 

The European Parliament's damp squib of a meeting with the Facebook boss revealed precious little about the social media giant - and arguably more about the EU body which invited him there in the first place. 

Mr Zuckerberg mouthed an apology to European consumers, promised to "do better" and leaned into his mantra about Facebook wanting to make the world a better place. 

Here's five things we learnt from Tuesday's session. 

1. Grilling? This was more of a stew

No wonder Mark Zuckerberg chose to appear before MEPs rather than MPs in Westminster.

European Parliament president Antonio Tajani’s decision to collect questions from MEPs all together before Mr Zuckerberg began answering made a mockery of what could have been a forensic analysis of one of the world’s most powerful companies, turning a potential grilling into more of a pulpy stew.

The MEP grouping heads spent more than one hour asking dozens of specific, detailed questions, as Zuckerberg scribbled notes onto his notepad. By the time they were done speaking, there was barely 20 minutes left for the Facebook boss to answer.

The fifth-richest man on the planet could barely suppress a smile as he told MEPs he would “try and answer as many of your questions as I can in the time we have.”

Instead of sweating out as he did at the US congress and senate, Mr Zuckerberg latched onto some talking points – AI, cyberbullying, even “well-being” – and neatly avoided all the thornier issues that MEPs had raised.

2. MEPs are far more tech-savvy than US senators

MEPs present in the room asked several detailed, pertinent and important questions of Facebook on Tuesday evening. Some focused on potential regulation – “we should not be asking companies [to remove content], we should be demanding it” – some probed into adherence to privacy laws, while others were more tech-specific, centring on so-called ‘shadow profiles’ and the way Facebook handled data belonging to non-users.

ALDE’s Guy Verhofstadt's line of questioning had an Orwellian streak to it. Would Mr Zuckerberg enter the internet pantheon of Steve Jobs and Bill Gates, he wondered, or would he end up as the genius who created “a digital monster?”

It all made for quite the change from some of the questions the Facebook guru faced on Capitol Hill last month, which included such gems as “If Facebook doesn’t charge users, how does it make money?”

What a shame they never got the answers they were hoping for.

3. Antitrust clouds are on Facebook’s horizon

The EU has never been shy of pushing the envelope when it comes to hitting big tech firms with its antitrust stick (just ask Microsoft or Google) and it might soon be Facebook’s turn.

Multiple MEPs asked questions about the need for regulation and hinted that they felt Facebook had grown just too big to handle. And while Mr Zuckerberg trotted out his standard line about Facebook being in favour of the “right” kind of regulation, he never had to venture beyond that truism – or even acknowledge questions about breaking up the social media behemoth [which counts Instagram, WhatsApp, Oculus and several other firms within its portfolio] at all.

4. Facebook’s commitment to new EU data privacy rules remains opaque

With the EU’s much-talked about GDPR directive just two days away from coming into force, several MEPs were understandably keen to understand just how closely Facebook was adhering to both the letter and spirit of the stringent law.

Mr Zuckerberg told MEPs that Facebook would be GDPR “compliant” by May 25, when the new rules come into force. But he did not answer questions about whether the tech giant was moving data belonging to non-European users off EU-based data centres to circumvent the law, or how the company planned on compensating EU citizens for data privacy breaches.

5. If you’re looking for transparency, don’t bother asking Antonio Tajani

The European Parliament president weaved and dodged journalists' questions about whose idea it was to have Mr Zuckerberg answer all MEPs’ questions in one go, and argued that it was hardly his fault that MEPs had spent over an hour asking their questions.

“Everyone knew the meeting would last until 7.30pm,” he said. “I didn’t receive any requests to hold a longer conference of presidents session.”

Within minutes, the memes and sarcastic tweets had started popping up on Twitter.

Perhaps the format – which prompted scoffs and guffaws from journalists in the Brussels parliament press room – was the reason Mr Tajani initially wanted to hold the meeting with Mr Zuckerberg behind closed doors?

With one of the world's most recognisable entrepreneurs sitting there ready to answer questions about one of the world's most ubiquitous software platforms, the European Parliament had a golden opportunity to reclaim credibility among EU voters and reassert its relevance as a political body. Instead, it blew it.