In fact, the two occurrences are not necessarily related, and may just be coincidental. You and your dentist probably made the right decision to temporize the original tooth until it appeared that the tooth and surrounding tissue was going to be all right. This would not necessarily add pressure to the adjacent tooth. Conversely, you likely treated the area with a little more care regarding chewy and hard foods than you would have otherwise. In addition, temporizing the tooth generally makes further treatment, if necessary, easier and less traumatic.
Large fillings can weaken the remaining tooth structure, causing the tooth to fracture.
This is why dentists will generally recommend a crown for a tooth that requires a large filling, either due to decay or trauma. This recommendation can be even more important for patients who clench or grind their teeth, as this action can cause cracks or fractures in teeth, especially those with fillings. There may be several approaches that can now be taken. Depending upon the condition of the tooth, no treatment may be necessary at this time. If the tooth remains symptomatic, contains decay, or interferes with function, treatment should be considered immediately.