As others have pointed out, it's not entirely about Intel doing badly, but rather Intel putting out a mediocre performance and AMD finally really succeeding.
And while the various technical reasons for that are interesting, I do think that at least some of the credit/blame needs to go to the leadership. AMD had a string of bad leadership that led to the company to near bankruptcy, but then they hired Lisa Su, who is basically a superstar engineer-turned-manager who has excelled in everything she's touched, from doing very low-level transistor research to being the leader of large teams (and now the entire company). At the same time, Intel hasn't actually had a good CEO for a long while now, with the top leadership in the company chasing the latest fads and spending billions on weird acquisitions that only get written off later, while the key areas of the business are not doing nearly as well as they did under their predecessors.
And while the various technical reasons for that are interesting, I do think that at least some of the credit/blame needs to go to the leadership. AMD had a string of bad leadership that led to the company to near bankruptcy, but then they hired Lisa Su, who is basically a superstar engineer-turned-manager who has excelled in everything she's touched, from doing very low-level transistor research to being the leader of large teams (and now the entire company). At the same time, Intel hasn't actually had a good CEO for a long while now, with the top leadership in the company chasing the latest fads and spending billions on weird acquisitions that only get written off later, while the key areas of the business are not doing nearly as well as they did under their predecessors.