Obama said "a politics of fear and resentment and retrenchment began to appear and that kind of politics is now on the move".
Obama also lamented that "the free press is under attack" at a time when Trump routinely complains about his coverage by "the fake news".
Tuesday's lecture was preceded by a panel discussion that featured former President Sirleaf, former United Nations Secretary-General Kofi Annan and the former Foreign Affairs Minister of Algeria Lakhdar Brahimi at the Obama Foundation gathering of young African leaders.
The President flip-flopped on his stance on the matter, having said a year ago he believed Russian Federation was behind the interference, but back-pedaling Monday to claim he believed Putin's account that Russian Federation was not involved.
"For a mother with a child in her arms, we can recognize that could be someone in my family, that could be my child", he added.
Mandela, who spent 27 years in prison and emerged to become South Africa's first black leader after white minority rule ended, died in December 2013 at the age of 95.
"Women in particular, by the way, I want you to get more involved", Obama said in footage shared by CNN. "But now if you catch them lying, they'll just keep on lying!"
He reminded the audience not to be too cynical, saying "We've been through darker times".
"I would like it to start here because the Eastern Cape is fertile of this agricultural revolution", he said.
"Obama said he can't believe it is necessary to once again speak up for equality and human rights", Stremlau said.
He added, "Don't you get a sense sometimes - again, I'm ad-libbing here - that these people who are so intent on putting people down and puffing themselves up that they're small-hearted, that there's something they're just afraid of?"
"Yesterday we had Trump and Putin standing together, now we are seeing the opposing team: Obama and Mandela", said Stremlau.
The former US president suggested a different path."Let me tell you what I believe", he said.
Without mentioning Trump by name, Obama said that we "are living in odd and uncertain times".
Land expropriation without compensation is one of the key programmes that will take forward former president Nelson Mandela's vision of a free South Africa, both President Cyril Ramaphosa and former president Jacob Zuma said on Wednesday.
In his speech Obama tracked the enormous social and democratic progress the world has made in the 100 years between Mandela's 1918 birth and 2018. Every generation has opportunity to remake the world...
Imprisoned for almost three decades for his fight against state-sanctioned racial segregation, he was freed in 1990 and quickly set about working to unite the nation through forgiveness and reconciliation, becoming South Africa's first black president.
Prince Harry visited Mandela's cell on the island during a 2015 trip to South Africa. He has at times eloquently attacked the "crude" identity politics that pits Americans against one another, but these flashes of brilliance were few and far between.