Why does bāʾ have qalqalah in الْمَبْثُوثِ?

Al-Qāriʿah and Az-Zalzalah — Comparative Tajwīd Practice

• Bāʾ is sākin and is a qalqalah letter
• Bāʾ has shaddah
• Hamzah follows bāʾ
• A sākin nūn follows bāʾ