Surge protectors, by design, incorporate a MOV (metal oxide varistor). Usually there are two, one between hot and ground, one between neutral and ground.
There is inevitably some leakage current, often a considerable amount (several mA).
Therefore, having many things with surge protectors plugged in can contribute to the total leakage current, and bring it close to or just beyond the trip point for the GFCI.
Also, since the MOVs will conduct electricity during voltage spikes (which is how they perform their surge protection function), any time there is such a spike, the GFCI will trip. Often, people plug in a "surge guard" power strip type device and then find they have nuisance trips during electrical storms.
Finally, MOVs, when the fail due to a large surge, will often have higher leakage current than they did previously.
Hope this helps.