Cristiano Ronaldo rounded off a fine individual week with a stunning 25-yard effort to open the scoring before Gareth Bale doubled Madrid's advantage from a free-kick with his first goal in two months.
Karim Benzema then registered his 100th goal for the club, whilst Angel di Maria and Alvaro Morata got their names on the scoresheet after the break to take Madrid level on points with Barcelona and Atletico Madrid at the top of Spain's La Liga. Defeat leaves Betis rooted to the foot of the table and without a win in 13 league games stretching back to September.
Ancelotti was pleased that despite the hosts' predicament, his side showed ruthless efficiency in front of goal to put them to the sword. "The games are easy in retrospect. Beforehand, every game can cause problems but we prepared well and played well."
Ancelotti had said prior to the game on Friday that Bale had still had progress to make after an injury disrupted start to his Real career. The Italian was much happier with the Welshman's contribution in Seville as he scored his tenth goal of the season.
And he reserved a special mention for Bale's former Tottenham Hotspur teammate Luka Modric, who once again excelled in midfield. "Bale played well, as did the whole team. We played with great quality and concentration throughout the game," he said.
"Ronaldo, Bale and Benzema were very efficient. The whole team gave them a lot of opportunities because we played with pace up front. We had a lot of chances and the help given by the midfielders, particularly Modric, was very good."
Victory means Madrid finished Saturday joint top of the table for the first time since mid-September. Barcelona and Atletico can reopen a three-point gap at the top should they beat Levante and Sevilla respectively on Sunday.
However, Ancelotti was pleased to have put the pressure on Real's title rivals. "This game was an important opportunity for us to go top of the table. It might be for just one night, but tonight we will sleep well."