It makes perfect sense, it is difficult to maintain the top four position without an overhaul in the main squad. The negative results obtained from Arsenal in a friendly match made anyone skeptical of Chelsea strength, especially Chelsea movement was very slow in the transfer market. The Premier League, which is inhabited by many big clubs, always provides high competition for the title, without a team reshuffle in the transfer window it is very difficult to compete at the top.
Premier League is very competitive and not many difference between clubs in top 4 or top 6. In last 3 seasons, only Manchester City and Liverpool have been dominating and outperforming in Premier League. They belong to top 2. For other clubs, their positions from the third to the sixth can be changed a lot between two seasons. Sometimes, being in top 4 and beyond top 4 is just a very small difference and can be decided in a final day. Leicester City lost their fourth position in 2 continuous seasons and in last season, they were not able to compete for top 4 with a very strong comeback of Arsenal and Tottenham.
Maybe from my observation Arsenal will be better than Chelsea next season, I doubt Chelsea will be able to maintain 3rd place next season, I am more optimistic that Arsenal will be a surprise team to occupy fourth place next season. Arteta has built a strong enough foundation from season to season, we can see developments in terms of transfers that Arsenal did this summer.
I agree because Arsenal has a better stability in their club. No change in ownership, same boss, same coach and same tactics. They only have changes in their players and their squad that were done to improve their quality.