It never changed. People have wanted to murder Biden. And Obama. And Bush. And Clinton. And Bush Sr. And Reagan. And Carter. etc. etc. etc. It's part of being the president, which is why the secret service exists. Just being such a public figure alone is enough to make you a target – Reagan was shot by some delusional guy to impress Jodie Foster.
And I'm sure there's tons more events we never heard about. Or people prevented from doing something just because there was enough security (who only needed to be present to prevent any attack).
For e.g. Obama there's an entire page: https://en.wikipedia.org/wiki/Security_incidents_involving_B...
and Bush: https://en.wikipedia.org/wiki/Security_incidents_involving_G...
And Trump: https://en.wikipedia.org/wiki/Security_incidents_involving_D...
And I'm sure there's tons more events we never heard about. Or people prevented from doing something just because there was enough security (who only needed to be present to prevent any attack).