Is it Biden's fault that the world is now in such a dangerous state?

Some of Donald Trump's former officials, such as General John Kelly, his former chief of staff, are saying the ex-president is a Fascist and a danger man who never listens. But others, such as Robert O'Brien, his former national security adviser, are saying that under Trump the world was a safer place. No wars. No invasion of Ukraine. No Middle East war. And that under Biden, his cautious, weak approach had been exploited to the full by, first the Taleban, then Putin and Xi Zinping, and Iran and, basically anyone with a grudge against the US. This is too simplistic. Even though the president of the United States has always been and is today a key figure in the way the world works it's far less so now and increasingly less so because of new alliances being formed against American domination, notably the one forged by Putin with China, India, Brazil and South Africa and others. But O'Brien is sure that if Trump had been in the White House in the last four years, Putin would not have been tempted to invade Ukraine. He says, in a piece in The New York Times, that Putin went for Ukraine because he took comfort from the chaotic withdrawal of US troops from Afghanistan under Biden's watch and thought he could get away with invading his neighbour without risking having a war with the US as a consequence. He was right. Biden sent billions and billions of dollars worth of weapons to Ukraine but made it clear from the start that he would never put American troops into Ukraine to fight Russian troops. Under the O'Brien thinking, Trump would have left that option in the air and it might have deterred Putin from invading at all. Who knows?