The reason was RedBull and a teammate called Webber who was like Bottas the last 2 years, just not good enough. Vettel is surely a (very) good driver and was lucky to be with the right team at the right moment, like Hamilton now. Basically they just need to beat their teammate to win the championship. Vettel almost gave away two championships to Alonso and Ferrari... RedBull was as dominant as Mercedes was the last 5 years. Was Alonso that good? Or Vettel not that good?

Okay, speaking about this year. I don't really see Vettel challanging Hamilton, because every year he is given away too many points due to his own mistakes. Last year Germany, France, Italy etc. If he can eliminate the mistakes than he might have a chance. The race in Australia is always special, Ferrari got a problem this year, also Hamilton. They will come back in Bahrain and China and after those races we can see clearer where this will lead in this year.

and another mistake by vettel... like i said few days ago . the race at all was very interesting and it was nice to see how good leclerc can be and how easy it was for him to follow and overtake vettel.

i dont think they will replace vettel very soon. they gonna run with both of them until mick schumacher i ready to replace vettel... so maybe 3 more years.

i really hope to see alonso back in red, very huge alonso fan since he joined f1 in minardi - long time ago -, but i dont see it happened. i think the only chance to see alonso back in f1 would be RedBull to replace gasly or something uncommon will happen