Boris Johnson managed to barely survive one scandal which was about lying about attending parties that violated COVID safety precautions. However, another, different scandal ended up bringing him down.
There were reports of drunken groping by an official in his administration. The uproar was more about the cover-up when Johnson said that he had no knowledge of the incident. It quickly became clear this was false.
In fact, he was aware of previous instances of similar behavior but still chose to give him a top-level, a number of his ministers resigned, forcing Johnson to announce his resignation as he no longer had enough support within his Party to be PM.
It's also worth mentioning that Johnson's standing had been slipping in public polls due to his numerous scandals and voter fatigue especially with voters focused on pocketbook issues. In recent elections, the Conservative Party lost seats. This contributed to conservatives pulling support, as they were willing to look past his issues when he was popular and delivering victories.
Johnson is expected to stay in office until October as the race begins to see who will replace him as the leader of the Conservative Party. The list of successors will first be narrowed down to 2, but the final selection will happen with a ballot among the Party's 180,000 members.
The current frontrunner is considered to be 42-year-old former Chancellor of the Exchequer, Rishi Sunak. He is attempting to run on a pro-immigrant message and touting his experience handling the economic portion of the pandemic.
At one time, he was considered to be Johnson's natural heir, but his popularity has dropped due to inflation, a slowing economy, and revelations about his wife not paying taxes.
Another candidate is Tom Tugendhat, the chairman of the Foreign Affairs Committee in the House of Commons. He has been a Johnson critic and his candidacy offers a 'clean start' to voters who are tired of Johnson's behavior. However, he is a relative novice in domestic politics with no natural base of support. Another potential liability in the Conservative Party is his opposition to Brexit.
Penny Mordaunt rose to prominence as a Johnson critic when she was fired 3 months into his administration as Defense Secretary. She has been a long-time Brexit supporter and is currently in second place according to recent polling.
She has yet to officially enter the race but has been very public in recent days, assuring the public that British institutions remain strong and that the country would get through this crisis.