#2 Becky Lynch appearance

Becky Lynch is suspended for 60 days but she still needs to make an appearance at Elimination Chamber.
Lynch is the biggest star in the company and audiences will give her a massive pop when she shows up. WWE needs Becky to get in Ronda Rousey's head ideally during her match with Ruby Riott, by appearing in the audience.
Female superstar says she inspired John Cena turning heel HERE
Lynch needs to play mind games with Rousey during her match, allowing Ruby Riott to take control of a distracted champion.
#1 Give time to the women's Elimination Chamber match

The women's tag-team elimination chamber match must be the main event as WWE is going to crown their 1st ever women's tag team champions.
Chamber matches are usually quite long so the company needs to avoid having too many other bouts on the card. The main event must be given the time it needs to make history.
A packed card is what WWE wants but the company needs to deviate from that and give the women the time they need to make history.