In the name of Allah,
Why is shahada placed first in the five pillars of islam? I got this question recently by my counterpart
Simply speaking as without performing, understanding its meaning and believing it you'll never be a Muslim.
So without the two testimonies الشهادات the shahaddatan all your worship is invane. As your prayer, your fast, your zakah and hajj won't be accepted.
Nevertheless be aware that the five pillars hadith is one hadith speaking about the most essential things that a Muslim should fulfill of which there are many with different content.