It was Hockey's performance in parliament, not someone "sending...

It was Hockey's performance in parliament, not someone "sending a Twitter" (they're called tweets), and it was the final straw not a single reason. Here's yet another article that explains the sequence of events:

Was GM Holden genuinely encouraged to stay?

Holden was the key. Toyota wanted to stay. The company had a viable export market to the Middle East, a robust business plan and most importantly, pride on the line.

Former Holden worker Shaun Matthews Photo: Darrian Traynor
Nowhere in the world had Toyota closed a fully-owned vehicle manufacturing plant and Australia was the first western country outside of Japan where Toyota chose to manufacture vehicles. Toyota just needed a viable supply chain, so the future of Holden and Toyota were linked.

As one car industry expert put it: "There was 100 years of samurai pride on the line."

September 2013 and the Coalition is elected with a commanding majority and the new Abbott government is in a hurry.

Its attention quickly turns to the future of the car manufacturing industry. Under the former Labor government Ford had already quit and incoming Prime Minister Tony Abbott is promising to slash $500 million in government funding from the auto industry.

By the following month Treasurer Joe Hockey has told the Productivity Commission to investigate Australia's automotive manufacturing industry, including "the long-term profitability, sustainability and productivity of the industry". The car industry was being audited.

In the lead up to the 2013 federal election, Holden presented a new business case to the Labor Government – an update on a March 2012 deal when Holden agreed to build the next generation Commodore and Cruze in Australia from 2016-2022 and the federal Government, Victorian Government and South Australian Government agreed to provide $275 million in assistance.

Then Industry Minister Kim Carr said there was not enough time to ratify a new deal on the updated business case with Holden before the 2013 election.

A few months later there is a new government. On October 2 that business case is again given to the government, specifically new Industry Minister Ian MacFarlane in the boardroom at Holden in Adelaide.One of those present at that meeting, South Australian Premier Jay Weatherill, says Holden wanted government assistance to continue.

"It was the ongoing support for automotive transformation that was the critical issue," he told Fairfax Media.
Weatherill says a deal could and should have been struck with Holden to extend the car industry for another decade. "It didn't need to fall off the edge of a cliff in the way in which it will and then having to rebuild something from the ashes."

Holden would not say how much government assistance was requested. But reports at the time suggest Holden needed an additional payment of between $150 million and $265 million to build the two new models in Australia.
What is clear is the new prime minister was in no mood for doubling down on the car industry. "There's not going to be any extra money over and above the generous support the taxpayers have been giving the motor industry for a long time," Mr Abbott said in early December 2013.

Then came the verbal assault from senior ministers days later in parliament, demanding Holden immediately announce its long term intentions.

"Either you're here or you're not," Treasurer Joe Hockey told parliament.

South Australian senator Nick Xenophon describes the comments as "taunting" Holden. "I think it was very much in the balance...but when General Motors in Detroit were being taunted, 'are you going to stay or are you going to go'... they thought 'why should we stay?'

"They [GM] were not going to be lectured to by the Australian government. It was completely unnecessary."

The ultimatum to Holden came despite the government not revealing its position publicly, having said it would wait for the Productivity Commission's findings – a preliminary report was to be released 10 days later – before making any funding decisions on the car industry.

GM Headquarters in Detroit decided it could take no more and announced it was quitting building cars in Australia 24 hours after the parliamentary assault. Toyota folded two months later.
http://www.smh.com.au/business/the-economy/who-killed-the-car-industry-20151112-gkx1c8.html